Skip ModuleInfo generation for C files (incl. *.i)

Fixes dmd-testsuite's compilable/testcomplex.i.

gen/modules.cpp

@@ -433,9 +433,11 @@ void codegenModule(IRState *irs, Module *m) {
 
   // Skip emission of all the additional module metadata if:
   // a) the -betterC switch is on,
-  // b) requested explicitly by the user via pragma(LDC_no_moduleinfo), or if
+  // b) requested explicitly by the user via pragma(LDC_no_moduleinfo),
-  // c) there's no ModuleInfo declaration.
+  // c) there's no ModuleInfo declaration, or if
-  if (global.params.useModuleInfo && !m->noModuleInfo && Module::moduleinfo) {
+  // d) the module is a C file.
+  if (global.params.useModuleInfo && !m->noModuleInfo && Module::moduleinfo &&
+      m->filetype != FileType::c) {
     // generate ModuleInfo
     registerModuleInfo(m);
   }

tests/dmd/runnable/cstuff3.i

@@ -1,3 +1,5 @@
+// REQUIRED_ARGS: -defaultlib=
+
 # 1 "runnable/extra-files/cstuff3.c"
 # 1 "<built-in>"
 # 1 "<command-line>"

tests/dmd/runnable/test23014.i

@@ -1,4 +1,5 @@
 /* EXTRA_SOURCES: imports/imp23014.i
+ * REQUIRED_ARGS: -defaultlib=
  */
 
 static _Thread_local int tmp;