wrappers: Use -lucrtapp instead of -lvcruntime140_app

Passing -lucrt* to the clang driver inhibits the implicit default
-lmsvcrt, so this ends up only using libucrtapp.a instead of libucrt.a.

This still requires that the default crt was ucrt, as the prebuilt
libc++.a needs to have been built for the right crt.

wrappers/clang-target-wrapper.c

@@ -192,8 +192,9 @@ int _tmain(int argc, TCHAR* argv[]) {
         exec_argv[arg++] = _T("-DUNICODE");
         // add the minimum runtime to use for UWP targets
         exec_argv[arg++] = _T("-Wl,-lwindowsapp");
-        // This requires that the default crt is ucrt.
-        exec_argv[arg++] = _T("-Wl,-lvcruntime140_app");
+        // This still requires that the toolchain (in particular, libc++.a) has
+        // been built targeting UCRT originally.
+        exec_argv[arg++] = _T("-Wl,-lucrtapp");
         // force the user of Universal C Runtime
         exec_argv[arg++] = _T("-D_UCRT");
     }

wrappers/clang-target-wrapper.sh

@@ -74,8 +74,9 @@ mingw32uwp)
     FLAGS="$FLAGS -DUNICODE"
     # add the minimum runtime to use for UWP targets
     FLAGS="$FLAGS -Wl,-lwindowsapp"
-    # This requires that the default crt is ucrt.
-    FLAGS="$FLAGS -Wl,-lvcruntime140_app"
+    # This still requires that the toolchain (in particular, libc++.a) has
+    # been built targeting UCRT originally.
+    FLAGS="$FLAGS -Wl,-lucrtapp"
     # Force the Universal C Runtime
     FLAGS="$FLAGS -D_UCRT"
     ;;

wrappers/ld-wrapper.sh

@@ -34,7 +34,7 @@ esac
 FLAGS="-m $M"
 case $TARGET_OS in
 mingw32uwp)
-    FLAGS="$FLAGS -lwindowsapp -lvcruntime140_app"
+    FLAGS="$FLAGS -lwindowsapp -lucrtapp"
     ;;
 esac
 ld.lld $FLAGS "$@"