mingw: Rename mingw32.lib to libmingw32.lib.

LLD expects the library file name (minus extension) to be exactly libmingw32. By
calling it mingw32 previously, we prevented it from being detected as being in
LLD's list of libraries that are excluded from the MinGW-specific auto-export
mechanism.

https://github.com/llvm/llvm-project/blob/b9d27ac252265839354fffeacaa8f39377ed7424/lld/COFF/MinGW.cpp#L30-L56

As a result, a DLL built for *-windows-gnu with Zig would export a bunch of
internal MinGW symbols. This sometimes worked out fine, but it could break at
link or run time when linking an EXE with a DLL, where both are targeting
*-windows-gnu and thus linking separate copies of mingw32.lib. In #23204, this
manifested as the linker getting confused about _gnu_exception_handler() because
it was incorrectly exported by the DLL while also being defined in the
mingw32.lib that was being linked into the EXE.

Closes #23204.

Author: alexrp

src/Compilation.zig

@@ -827,7 +827,7 @@ pub const MiscTask = enum {
 
     @"mingw-w64 crt2.o",
     @"mingw-w64 dllcrt2.o",
-    @"mingw-w64 mingw32.lib",
+    @"mingw-w64 libmingw32.lib",
 };
 
 pub const MiscError = struct {
@@ -1886,7 +1886,7 @@ pub fn create(gpa: Allocator, arena: Allocator, options: CreateOptions) !*Compil
 
                     const main_crt_file: mingw.CrtFile = if (is_dyn_lib) .dllcrt2_o else .crt2_o;
                     comp.queued_jobs.mingw_crt_file[@intFromEnum(main_crt_file)] = true;
-                    comp.queued_jobs.mingw_crt_file[@intFromEnum(mingw.CrtFile.mingw32_lib)] = true;
+                    comp.queued_jobs.mingw_crt_file[@intFromEnum(mingw.CrtFile.libmingw32_lib)] = true;
                     comp.remaining_prelink_tasks += 2;
 
                     // When linking mingw-w64 there are some import libs we always need.

src/link/Coff.zig

@@ -2104,7 +2104,7 @@ fn linkWithLLD(coff: *Coff, arena: Allocator, tid: Zcu.PerThread.Id, prog_node:
                             try argv.append(try comp.crtFileAsString(arena, "crt2.obj"));
                         }
 
-                        try argv.append(try comp.crtFileAsString(arena, "mingw32.lib"));
+                        try argv.append(try comp.crtFileAsString(arena, "libmingw32.lib"));
                     } else {
                         const lib_str = switch (comp.config.link_mode) {
                             .dynamic => "",

src/mingw.zig

@@ -14,7 +14,7 @@ const dev = @import("dev.zig");
 pub const CrtFile = enum {
     crt2_o,
     dllcrt2_o,
-    mingw32_lib,
+    libmingw32_lib,
 };
 
 /// TODO replace anyerror with explicit error set, recording user-friendly errors with
@@ -69,7 +69,7 @@ pub fn buildCrtFile(comp: *Compilation, crt_file: CrtFile, prog_node: std.Progre
             });
         },
 
-        .mingw32_lib => {
+        .libmingw32_lib => {
             var c_source_files = std.ArrayList(Compilation.CSourceFile).init(arena);
 
             {
@@ -173,7 +173,7 @@ pub fn buildCrtFile(comp: *Compilation, crt_file: CrtFile, prog_node: std.Progre
                 }
             }
 
-            return comp.build_crt_file("mingw32", .Lib, .@"mingw-w64 mingw32.lib", prog_node, c_source_files.items, .{
+            return comp.build_crt_file("libmingw32", .Lib, .@"mingw-w64 libmingw32.lib", prog_node, c_source_files.items, .{
                 .unwind_tables = unwind_tables,
                 // https://github.com/llvm/llvm-project/issues/43698#issuecomment-2542660611
                 .allow_lto = false,