Add test for ucrt64 toolchain detection on fedora

ucrt64-toolchain/main.fmf

@@ -0,0 +1,12 @@
+summary: Test that ucrt64 toolchain is detected
+test: ./runtest.sh
+component:
+  - clang
+require:
+  - clang
+  - ucrt64-gcc-c++
+
+adjust:
+  - enabled: false
+    when: distro != fedora or distro < fedora-37
+    because: "The ucrt64 toolchain is only available since Fedora 37"

ucrt64-toolchain/runtest.sh

@@ -0,0 +1,4 @@
+set -eux
+
+clang++ --target=x86_64-windows-gnu test.cpp
+file a.exe | grep "PE32+ executable (console) x86-64, for MS Windows"

ucrt64-toolchain/test.cpp

@@ -0,0 +1,6 @@
+#include <iostream>
+
+int main() {
+    std::cout << "Hello world" << std::endl;
+    return 0;
+}