Add testcase for mixed C and D compilation

test cases/d/3 mixed/app.d

@@ -0,0 +1,8 @@
+
+extern(C) int printLibraryString(const char *str);
+
+void main ()
+{
+    immutable ret = printLibraryString ("C foo");
+    assert (ret == 3);
+}

test cases/d/3 mixed/installed_files.txt

@@ -0,0 +1,4 @@
+usr/bin/appdc_d?exe
+usr/lib/libstuff.so
+usr/bin/appdc_s?exe
+usr/lib/libstuff.a

test cases/d/3 mixed/libstuff.c

@@ -0,0 +1,18 @@
+#if defined _WIN32 || defined __CYGWIN__
+  #define DLL_PUBLIC __declspec(dllexport)
+#else
+  #if defined __GNUC__
+    #define DLL_PUBLIC __attribute__ ((visibility("default")))
+  #else
+    #pragma message ("Compiler does not support symbol visibility.")
+    #define DLL_PUBLIC
+  #endif
+#endif
+
+#include <stdio.h>
+
+int DLL_PUBLIC printLibraryString(const char *str)
+{
+    printf("C library says: %s", str);
+    return 3;
+}

test cases/d/3 mixed/meson.build

@@ -0,0 +1,9 @@
+project('Mixing C and D', 'd', 'c')
+
+ldyn = shared_library('stuff', 'libstuff.c', install : true)
+ed = executable('appdc_d', 'app.d', link_with : ldyn, install : true)
+test('linktest_cdyn', ed)
+
+lstatic = static_library('stuff', 'libstuff.c', install : true)
+es = executable('appdc_s', 'app.d', link_with : lstatic, install : true)
+test('linktest_cstatic', es)