Only populate rc_include_dirs if there are .rc files in the compilation

Author: squeek502

src/Compilation.zig

@@ -1001,15 +1001,24 @@ pub fn create(gpa: Allocator, options: InitOptions) !*Compilation {
             options.libc_installation,
         );
 
-        // .rc preprocessor needs to know the libc dirs even if we are not linking libc
-        const rc_dirs = try detectLibCIncludeDirs(
-            arena,
-            options.zig_lib_directory.path.?,
-            options.target,
-            options.is_native_abi,
-            true,
-            options.libc_installation,
-        );
+        // If we have .rc files to compile, then the .rc preprocessor needs
+        // to know the libc dirs even if we are not linking libc
+        const rc_dirs = if (options.rc_source_files.len > 0)
+            try detectLibCIncludeDirs(
+                arena,
+                options.zig_lib_directory.path.?,
+                options.target,
+                options.is_native_abi,
+                true,
+                options.libc_installation,
+            )
+        else
+            LibCDirs{
+                .libc_include_dir_list = &[0][]u8{},
+                .libc_installation = null,
+                .libc_framework_dir_list = &.{},
+                .sysroot = null,
+            };
 
         const sysroot = options.sysroot orelse libc_dirs.sysroot;