test cases: Add test ensuring that -include in gcc won't break pch

This is just forcing the usage of -include as c_args, even though this
particular case can happen easily when this is provided via a dependency
cflags.

We also ensure that both the headers are included by using locale
definitions.

test cases/common/13 pch/meson.build

@@ -13,6 +13,7 @@ subdir('cpp')
 subdir('generated')
 subdir('userDefined')
 subdir('withIncludeDirectories')
+subdir('withIncludeFile')
 
 if meson.backend() == 'xcode'
   warning('Xcode backend only supports one precompiled header per target. Skipping "mixed" which has various precompiled headers.')

test cases/common/13 pch/withIncludeFile/meson.build

@@ -0,0 +1,18 @@
+cc = meson.get_compiler('c')
+cc_id = cc.get_id()
+
+if cc_id == 'lcc'
+  error('MESON_SKIP_TEST: Elbrus compiler does not support PCH.')
+endif
+
+if cc.get_argument_syntax() == 'gcc'
+  c_args = ['-include', 'locale.h']
+elif cc.get_argument_syntax() == 'msvc'
+  c_args = ['/FI' + 'locale.h']
+else
+  subdir_done()
+endif
+
+exe = executable('prog', 'prog.c',
+c_args: c_args,
+c_pch : 'pch/prog.h')

test cases/common/13 pch/withIncludeFile/pch/prog.h

@@ -0,0 +1,6 @@
+#ifndef PROG_H
+// Header guards for PCH confuse msvc in some situations.
+// Using them here makes sure we handle this correctly.
+#define PROG_H
+#include<stdio.h>
+#endif

test cases/common/13 pch/withIncludeFile/prog.c

@@ -0,0 +1,11 @@
+// No includes here, they need to come from the PCH or explicit inclusion
+
+void func(void) {
+    fprintf(stdout, "This is a function that fails if stdio is not #included.\n");
+    setlocale(LC_ALL, ""); /* This will fail if locale.h is not included */
+}
+
+int main(void) {
+    return 0;
+}
+