make "gnu" (mingw-w64) the default C ABI on Windows

Closes #6565

Author: andrewrk

lib/std/target.zig

@@ -498,8 +498,8 @@ pub const Target = struct {
                 .netbsd,
                 .hurd,
                 .haiku,
-                => return .gnu,
                 .windows,
+                => return .gnu,
                 .uefi,
                 => return .msvc,
                 .linux,
@@ -1258,15 +1258,18 @@ pub const Target = struct {
         return linuxTripleSimple(allocator, self.cpu.arch, self.os.tag, self.abi);
     }
 
-    pub fn oFileExt_cpu_arch_abi(cpu_arch: Cpu.Arch, abi: Abi) [:0]const u8 {
-        switch (abi) {
-            .msvc => return ".obj",
+    pub fn oFileExt_os_abi(os_tag: Os.Tag, abi: Abi) [:0]const u8 {
+        if (abi == .msvc) {
+            return ".obj";
+        }
+        switch (os_tag) {
+            .windows, .uefi => return ".obj",
             else => return ".o",
         }
     }
 
     pub fn oFileExt(self: Target) [:0]const u8 {
-        return oFileExt_cpu_arch_abi(self.cpu.arch, self.abi);
+        return oFileExt_os_abi(self.os.tag, self.abi);
     }
 
     pub fn exeFileExtSimple(cpu_arch: Cpu.Arch, os_tag: Os.Tag) [:0]const u8 {
@@ -1285,30 +1288,36 @@ pub const Target = struct {
         return exeFileExtSimple(self.cpu.arch, self.os.tag);
     }
 
-    pub fn staticLibSuffix_cpu_arch_abi(cpu_arch: Cpu.Arch, abi: Abi) [:0]const u8 {
-        switch (abi) {
-            .msvc => return ".lib",
+    pub fn staticLibSuffix_os_abi(os_tag: Os.Tag, abi: Abi) [:0]const u8 {
+        if (abi == .msvc) {
+            return ".lib";
+        }
+        switch (os_tag) {
+            .windows, .uefi => return ".lib",
             else => return ".a",
         }
     }
 
     pub fn staticLibSuffix(self: Target) [:0]const u8 {
-        return staticLibSuffix_cpu_arch_abi(self.cpu.arch, self.abi);
+        return staticLibSuffix_os_abi(self.os.tag, self.abi);
     }
 
     pub fn dynamicLibSuffix(self: Target) [:0]const u8 {
         return self.os.tag.dynamicLibSuffix();
     }
 
-    pub fn libPrefix_cpu_arch_abi(cpu_arch: Cpu.Arch, abi: Abi) [:0]const u8 {
-        switch (abi) {
-            .msvc => return "",
+    pub fn libPrefix_os_abi(os_tag: Os.Tag, abi: Abi) [:0]const u8 {
+        if (abi == .msvc) {
+            return "";
+        }
+        switch (os_tag) {
+            .windows, .uefi => return "",
             else => return "lib",
         }
     }
 
     pub fn libPrefix(self: Target) [:0]const u8 {
-        return libPrefix_cpu_arch_abi(self.cpu.arch, self.abi);
+        return libPrefix_os_abi(self.os.tag, self.abi);
     }
 
     pub fn getObjectFormatSimple(os_tag: Os.Tag, cpu_arch: Cpu.Arch) ObjectFormat {

lib/std/zig/cross_target.zig

@@ -473,23 +473,23 @@ pub const CrossTarget = struct {
     }
 
     pub fn oFileExt(self: CrossTarget) [:0]const u8 {
-        return Target.oFileExt_cpu_arch_abi(self.getCpuArch(), self.getAbi());
+        return Target.oFileExt_os_abi(self.getOsTag(), self.getAbi());
     }
 
     pub fn exeFileExt(self: CrossTarget) [:0]const u8 {
         return Target.exeFileExtSimple(self.getCpuArch(), self.getOsTag());
     }
 
     pub fn staticLibSuffix(self: CrossTarget) [:0]const u8 {
-        return Target.staticLibSuffix_cpu_arch_abi(self.getCpuArch(), self.getAbi());
+        return Target.staticLibSuffix_os_abi(self.getOsTag(), self.getAbi());
     }
 
     pub fn dynamicLibSuffix(self: CrossTarget) [:0]const u8 {
         return self.getOsTag().dynamicLibSuffix();
     }
 
     pub fn libPrefix(self: CrossTarget) [:0]const u8 {
-        return Target.libPrefix_cpu_arch_abi(self.getCpuArch(), self.getAbi());
+        return Target.libPrefix_os_abi(self.getOsTag(), self.getAbi());
     }
 
     pub fn isNativeCpu(self: CrossTarget) bool {

src/Compilation.zig

@@ -3168,7 +3168,7 @@ fn detectLibCIncludeDirs(
 
     // If linking system libraries and targeting the native abi, default to
     // using the system libc installation.
-    if (link_system_libs and is_native_abi) {
+    if (link_system_libs and is_native_abi and !target.isMinGW()) {
         const libc = try arena.create(LibCInstallation);
         libc.* = try LibCInstallation.findNative(.{ .allocator = arena, .verbose = true });
         return detectLibCFromLibCInstallation(arena, target, libc);

src/libc_installation.zig

@@ -8,7 +8,6 @@ const build_options = @import("build_options");
 
 const is_darwin = Target.current.isDarwin();
 const is_windows = Target.current.os.tag == .windows;
-const is_gnu = Target.current.isGnu();
 const is_haiku = Target.current.os.tag == .haiku;
 
 const log = std.log.scoped(.libc_installation);
@@ -100,14 +99,14 @@ pub const LibCInstallation = struct {
             log.err("crt_dir may not be empty for {s}\n", .{@tagName(Target.current.os.tag)});
             return error.ParseError;
         }
-        if (self.msvc_lib_dir == null and is_windows and !is_gnu) {
+        if (self.msvc_lib_dir == null and is_windows) {
             log.err("msvc_lib_dir may not be empty for {s}-{s}\n", .{
                 @tagName(Target.current.os.tag),
                 @tagName(Target.current.abi),
             });
             return error.ParseError;
         }
-        if (self.kernel32_lib_dir == null and is_windows and !is_gnu) {
+        if (self.kernel32_lib_dir == null and is_windows) {
             log.err("kernel32_lib_dir may not be empty for {s}-{s}\n", .{
                 @tagName(Target.current.os.tag),
                 @tagName(Target.current.abi),