Add wrappers that target Universal Windows

wrappers/clang-target-wrapper.c

@@ -257,6 +257,9 @@ int _tmain(int argc, TCHAR* argv[]) {
     dash = _tcschr(arch, '-');
     if (dash)
         *dash = '\0';
+    TCHAR *target_os = _tcsrchr(target, '-');
+    if (target_os)
+        target_os++;
 
     // Check if trying to compile Ada; if we try to do this, invoking clang
     // would end up invoking <triplet>-gcc with the same arguments, which ends
@@ -293,6 +296,15 @@ int _tmain(int argc, TCHAR* argv[]) {
         // Dwarf is the default here.
     }
 
+    if (target_os && !_tcscmp(target_os, _T("mingw32uwp"))) {
+        // the UWP target is for Windows 10
+        exec_argv[arg++] = _T("-D_WIN32_WINNT=0x0A00 -DWINVER=0x0A00");
+        // the UWP target can only use Windows Store APIs
+        exec_argv[arg++] = _T("-DWINAPI_FAMILY=WINAPI_FAMILY_APP");
+        // the Windows Store API only supports Windows Unicode (some rare ANSI ones are available)
+        exec_argv[arg++] = _T("-DUNICODE");
+    }
+
     exec_argv[arg++] = _T("-target");
     exec_argv[arg++] = target;
     exec_argv[arg++] = _T("-rtlib=compiler-rt");