Remove support for mingw32 and mingw64

Official support for msvcrt-6 used by mingw32 and mingw64 was dropped in ruby core:
  ruby/ruby@cdb9893

mingw64 was no longer in use, since rubyinstaller-3.1 and it fails now with:
```
  ld.exe: .rsrc merge failure: duplicate leaf: type: 18 (MANIFEST) name: 2 lang: 409
```

mingw32 fails with:
```
./miniruby.exe -I../snapshot-master/lib -I. -I.ext/common  ../snapshot-master/tool/generic_erb.rb -o builtin_binary.rbbin \
	../snapshot-master/template/builtin_binary.rbbin.tmpl
../snapshot-master/tool/generic_erb.rb:30: [BUG] Segmentation fault
ruby 4.0.0dev (2025-11-19 master 7840ef2f43) +PRISM [i386-mingw32]

-- Control frame information -----------------------------------------------
c:0005 p:---- s:0028 e:000027 l:y b:---- CFUNC  :read
c:0004 p:0010 s:0023 e:000020 l:n b:---- BLOCK  ../snapshot-master/tool/generic_erb.rb:30 [FINISH]
c:0003 p:---- s:0016 e:000015 l:y b:---- CFUNC  :map
c:0002 p:0075 s:0012 E:0015c0 l:n b:---- EVAL   ../snapshot-master/tool/generic_erb.rb:29 [FINISH]
c:0001 p:0000 s:0003 E:002040 l:y b:---- DUMMY  [FINISH]

-- Ruby level backtrace information ----------------------------------------
../snapshot-master/tool/generic_erb.rb:29:in '<main>'
../snapshot-master/tool/generic_erb.rb:29:in 'map'
../snapshot-master/tool/generic_erb.rb:30:in 'block in <main>'
../snapshot-master/tool/generic_erb.rb:30:in 'read'

-- Threading information ---------------------------------------------------
Total ractor count: 1
Ruby thread count for this ractor: 1

-- C level backtrace information -------------------------------------------
C:\Windows\SYSTEM32\ntdll.dll(ZwWaitForSingleObject+0xc) [0x7743905c]
C:\Windows\System32\KERNELBASE.dll(WaitForSingleObject+0x12) [0x75028412]
D:\a\rubyinstaller2-packages\rubyinstaller2-packages\mingw-w64-ruby-head\src\build-MINGW32\miniruby.exe(rb_obj_shape_id+0xc8bd9) [0x0053bad9]
D:\a\rubyinstaller2-packages\rubyinstaller2-packages\mingw-w64-ruby-head\src\build-MINGW32\miniruby.exe(rb_obj_shape_id+0xa8011) [0x0051af11]
D:\a\rubyinstaller2-packages\rubyinstaller2-packages\mingw-w64-ruby-head\src\build-MINGW32\miniruby.exe(rb_obj_shape_id+0xc39fe) [0x005368fe]
C:\Windows\SYSTEM32\ntdll.dll(RtlInitializeExceptionChain+0xfd) [0x7742d76d]
```

RubyInstaller-4.0 will drop x86 (32-bit) support therefore.

Author: larskanis

.github/workflows/ci.yml

@@ -15,10 +15,6 @@ jobs:
       fail-fast: false
       matrix:
         include:
-        - MINGW_ARCH: "mingw32"
-          RUNON: windows-latest
-        - MINGW_ARCH: "mingw64"
-          RUNON: windows-latest
         - MINGW_ARCH: "ucrt64"
           RUNON: windows-latest
         - MINGW_ARCH: "clangarm64"

mingw-w64-ruby-head/PKGBUILD

@@ -8,7 +8,7 @@ pkgver() {
 pkgrel=1
 pkgdesc="An object-oriented language for quick and easy programming (mingw-w64)"
 arch=('any')
-mingw_arch=('mingw32' 'mingw64' 'ucrt64' 'clangarm64')
+mingw_arch=('ucrt64' 'clangarm64')
 url="https://www.ruby-lang.org/en"
 license=("BSD, custom")
 makedepends=("${MINGW_PACKAGE_PREFIX}-cc"