Fix static linking when using MinGW-w64

.github/workflows/mingw-w64.yml

@@ -80,7 +80,7 @@ jobs:
         shell: msys2 {0}
         run: |
           mkdir bin
-          cc crystal.obj -o bin/crystal.exe \
+          cc crystal.obj -o bin/crystal.exe -mcrtdll=ucrt -municode \
             $(pkg-config bdw-gc libpcre2-8 iconv zlib libffi --libs) \
             $(llvm-config --libs --system-libs --ldflags) \
             -lDbgHelp -lole32 -lWS2_32 -Wl,--stack,0x800000

src/compiler/crystal/loader/mingw.cr

@@ -27,6 +27,7 @@ class Crystal::Loader
     libnames = [] of String
     file_paths = [] of String
     extra_search_paths = [] of String
+    crt_dll = "msvcrt"
 
     OptionParser.parse(args.dup) do |parser|
       parser.on("-L DIRECTORY", "--library-path DIRECTORY", "Add DIRECTORY to library search path") do |directory|
@@ -39,17 +40,21 @@ class Crystal::Loader
         raise LoadError.new "static libraries are not supported by Crystal's runtime loader"
       end
       parser.unknown_args do |args, after_dash|
-        file_paths.concat args
+        file_paths.concat args.reject(&.starts_with?("-mcrtdll="))
       end
 
       parser.invalid_option do |arg|
-        unless arg.starts_with?("-Wl,")
+        if crt_dll_arg = arg.lchop?("-mcrtdll=")
+          # the GCC spec is `%{!mcrtdll=*:-lmsvcrt} %{mcrtdll=*:-l%*}`
+          crt_dll = crt_dll_arg
+        elsif !arg.starts_with?("-Wl,")
           raise LoadError.new "Not a recognized linker flag: #{arg}"
         end
       end
     end
 
     search_paths = extra_search_paths + search_paths
+    libnames << crt_dll
 
     begin
       loader = new(search_paths)

src/crystal/system/win32/wmain.cr

@@ -2,14 +2,12 @@ require "c/stringapiset"
 require "c/winnls"
 require "c/stdlib"
 
-{% begin %}
-  # we have both `main` and `wmain`, so we must choose an unambiguous entry point
+# we have both `main` and `wmain`, so we must choose an unambiguous entry point
+{% if flag?(:msvc) %}
   @[Link({{ flag?(:static) ? "libcmt" : "msvcrt" }})]
-  {% if flag?(:msvc) %}
-    @[Link(ldflags: "/ENTRY:wmainCRTStartup")]
-  {% elsif flag?(:gnu) && !flag?(:interpreted) %}
-    @[Link(ldflags: "-municode")]
-  {% end %}
+  @[Link(ldflags: "/ENTRY:wmainCRTStartup")]
+{% elsif flag?(:gnu) && !flag?(:interpreted) %}
+  @[Link(ldflags: "-municode")]
 {% end %}
 lib LibCrystalMain
 end

src/empty.cr

@@ -1,6 +1,6 @@
 require "primitives"
 
-{% if flag?(:win32) %}
+{% if flag?(:msvc) %}
   @[Link({{ flag?(:static) ? "libcmt" : "msvcrt" }})] # For `mainCRTStartup`
 {% end %}
 lib LibCrystalMain

src/lib_c.cr

@@ -1,5 +1,7 @@
-{% if flag?(:win32) %}
+{% if flag?(:msvc) %}
   @[Link({{ flag?(:static) ? "libucrt" : "ucrt" }})]
+{% elsif flag?(:win32) && flag?(:gnu) %}
+  @[Link(ldflags: "-mcrtdll=ucrt")]
 {% end %}
 lib LibC
   alias Char = UInt8