[tests] Add tests for c/cpp standard regressions

Author: tobil4sk

.github/workflows/test.yml

@@ -233,4 +233,8 @@ jobs:
           haxe: ${{ inputs.haxe }}
       - name: test c/cxx_standard attributes
         working-directory: test/cxx_standard
-        run: haxelib run hxcpp Build.xml
+        run: |
+          for xml in *.xml; do
+            haxelib run hxcpp $xml
+            haxelib run hxcpp $xml clean
+          done

test/cxx_standard/Build_legacy.xml

@@ -0,0 +1,12 @@
+<xml>
+	<set name="HXCPP_CPP17" value="1" />
+
+	<files id="test">
+		<compilerflag value="/Zc:__cplusplus" if="isMsvc" />
+		<file name="main.cpp" />
+	</files>
+
+	<target id="default" tool="linker" toolid="exe" output="main">
+		<files id="test"/>
+	</target>
+</xml>

test/cxx_standard/Build_section.xml

@@ -0,0 +1,12 @@
+<xml>
+	<files id="test" cxx_standard="17">
+		<compilerflag value="/Zc:__cplusplus" if="isMsvc" />
+		<section>
+			<file name="main.cpp" />
+		</section>
+	</files>
+
+	<target id="default" tool="linker" toolid="exe" output="main">
+		<files id="test"/>
+	</target>
+</xml>