Cannot install bcrypt 3.1.16 gem on Windows: ld.exe: cannot find -lgmp

Question

I'm trying to update my bundle, it needs bcrypt, but it fails with an error.

>bundle
Fetching bcrypt 3.1.16
Installing bcrypt 3.1.16 with native extensions
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    current directory: C:/ruby24/lib/ruby/gems/2.4.0/gems/bcrypt-3.1.16/ext/mri
C:/ruby24/bin/ruby.exe -r ./siteconf20201016-19812-xjdoy9.rb extconf.rb
creating Makefile

current directory: C:/ruby24/lib/ruby/gems/2.4.0/gems/bcrypt-3.1.16/ext/mri
make "DESTDIR=" clean

current directory: C:/ruby24/lib/ruby/gems/2.4.0/gems/bcrypt-3.1.16/ext/mri
make "DESTDIR="
generating bcrypt_ext-x64-mingw32.def
compiling bcrypt_ext.c
compiling crypt_blowfish.c
x86_64-w64-mingw32-gcc  -D__SKIP_GNU -D_FORTIFY_SOURCE=2
-D__USE_MINGW_ANSI_STDIO=1 -DFD_SETSIZE=2048 -D_WIN32_WINNT=0x0501
-D__MINGW_USE_VC2005_COMPAT -D_FILE_OFFSET_BITS=64   -c -o x86.o x86.S
compiling crypt_gensalt.c
compiling wrapper.c
wrapper.c:182:60: warning: 'struct crypt_data' declared inside parameter list
[enabled by default]
wrapper.c:182:60: warning: its scope is only this definition or declaration,
which is probably not what you want [enabled by default]
linking shared-object bcrypt_ext.so
c:/devkit2/mingw/bin/../lib/gcc/x86_64-w64-mingw32/4.7.2/../../../../x86_64-w64-mingw32/bin/ld.exe:
cannot find -lgmp
collect2.exe: error: ld returned 1 exit status
make: *** [bcrypt_ext.so] Error 1

make failed, exit code 2

Gem files will remain installed in
C:/ruby24/lib/ruby/gems/2.4.0/gems/bcrypt-3.1.16 for inspection.
Results logged to
C:/ruby24/lib/ruby/gems/2.4.0/extensions/x64-mingw32/2.4.0/bcrypt-3.1.16/gem_make.out

An error occurred while installing bcrypt (3.1.16), and Bundler cannot continue.
Make sure that `gem install bcrypt -v '3.1.16' --source 'https://rubygems.org/'`
succeeds before bundling.

In Gemfile:
  devise was resolved to 4.7.3, which depends on
    bcrypt

It fails during make

C:\ruby24\lib\ruby\gems\2.4.0\gems\bcrypt-3.1.16\ext\mri>make
linking shared-object bcrypt_ext.so
c:/devkit2/mingw/bin/../lib/gcc/x86_64-w64-mingw32/4.7.2/../../../../x86_64-w64-mingw32/bin/ld.exe: cannot find -lgmp
collect2.exe: error: ld returned 1 exit status
make: *** [bcrypt_ext.so] Error 1

This is what ld -lgmp --verbose gives

C:\ruby24\lib\ruby\gems\2.4.0\gems\bcrypt-3.1.16\ext\mri>ld -lgmp --verbose
GNU ld (rubenvb-4.7.2-release) 2.23.51.20120920
  Supported emulations:
   i386pep
   i386pe
using internal linker script:
==================================================
/* Default linker script, for normal executables */
OUTPUT_FORMAT(pei-x86-64)
SEARCH_DIR("=/usr/local/lib"); SEARCH_DIR("=/lib"); SEARCH_DIR("=/usr/lib");
SECTIONS
{
  /* Make the virtual address and file offset synced if the alignment is
     lower than the target page size. */
  . = SIZEOF_HEADERS;
  . = ALIGN(__section_alignment__);
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  {
     *(.init)
    *(.text)
    *(SORT(.text$*))
     *(.text.*)
     *(.gnu.linkonce.t.*)
    *(.glue_7t)
    *(.glue_7)
    . = ALIGN(8);
     ___CTOR_LIST__ = .; __CTOR_LIST__ = . ;
                        LONG (-1); LONG (-1);*(.ctors); *(.ctor); *(SORT(.ctors.*));  LONG (0); LONG (0);
     ___DTOR_LIST__ = .; __DTOR_LIST__ = . ;
                        LONG (-1); LONG (-1); *(.dtors); *(.dtor); *(SORT(.dtors.*));  LONG (0); LONG (0);
     *(.fini)
    /* ??? Why is .gcc_exc here?  */
     *(.gcc_exc)
    PROVIDE (etext = .);
     *(.gcc_except_table)
  }
  /* The Cygwin32 library uses a section to avoid copying certain data
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     breaks building the cygwin32 dll.  Instead, we name the section
     ".data_cygwin_nocopy" and explicitly include it after __data_end__. */
  .data BLOCK(__section_alignment__) :
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    __data_start__ = . ;
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  }
  __rt_psrelocs_size = __rt_psrelocs_end - __rt_psrelocs_start;
  ___RUNTIME_PSEUDO_RELOC_LIST_END__ = .;
  __RUNTIME_PSEUDO_RELOC_LIST_END__ = .;
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  __RUNTIME_PSEUDO_RELOC_LIST__ = . - __rt_psrelocs_size;
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    PROVIDE (end = .);
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}


==================================================
attempt to open /home/ruben/mingw-w64/mingw64mingw64/mingw64/usr/local/lib/libgmp.dll.a failed
attempt to open /home/ruben/mingw-w64/mingw64mingw64/mingw64/usr/local/lib/gmp.dll.a failed
attempt to open /home/ruben/mingw-w64/mingw64mingw64/mingw64/usr/local/lib/libgmp.a failed
attempt to open /home/ruben/mingw-w64/mingw64mingw64/mingw64/usr/local/lib/gmp.lib failed
attempt to open /home/ruben/mingw-w64/mingw64mingw64/mingw64/usr/local/lib/libgmp.dll failed
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attempt to open /home/ruben/mingw-w64/mingw64mingw64/mingw64/usr/local/lib\libgmp.a failed
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attempt to open /home/ruben/mingw-w64/mingw64mingw64/mingw64/usr/lib/libgmp.dll.a failed
attempt to open /home/ruben/mingw-w64/mingw64mingw64/mingw64/usr/lib/gmp.dll.a failed
attempt to open /home/ruben/mingw-w64/mingw64mingw64/mingw64/usr/lib/libgmp.a failed
attempt to open /home/ruben/mingw-w64/mingw64mingw64/mingw64/usr/lib/gmp.lib failed
attempt to open /home/ruben/mingw-w64/mingw64mingw64/mingw64/usr/lib/libgmp.dll failed
attempt to open /home/ruben/mingw-w64/mingw64mingw64/mingw64/usr/lib/gmp.dll failed
attempt to open /home/ruben/mingw-w64/mingw64mingw64/mingw64/usr/lib\gmp.lib failed
ld: cannot find -lgmp

Windows 8.1, Ruby 2.4

>ridk version
---
ruby:
  path: C:/ruby24
  version: 2.4.3
  platform: x64-mingw32
ruby_installer:
  package_version: 2.4.3-1
  git_commit: 36aac73
msys2:
  path: C:\msys64
  title: MSYS2 64bit
  version: '20161025'
cc: x86_64-w64-mingw32-gcc (rubenvb-4.7.2-release) 4.7.2
sh: GNU bash, version 4.3.46(2)-release (x86_64-pc-msys)
os: Microsoft Windows [Version 6.3.9600]

Answer 1

I had an old version of MSYS2, which Ruby uses to build native C++ gems. I deleted my old \msys64 directory, reinstalled it with Chocolatey (choco install msys2), used ridk install to install the build tools, and it was able to compile bcrypt gem.