Try building a hello world example

Dockerfile

@@ -234,3 +234,7 @@ ENV ASCPP="gas-preprocessor.pl ${CC}"
 ENV CCAS="gas-preprocessor.pl ${CC}"
 ENV LDFLAGS="-lmsvcr120_app ${LDFLAGS}"
 
+RUN mkdir -p /build/hello
+COPY hello.c /build/hello/
+RUN cd /build/hello && armv7-w64-mingw32-clang hello.c -o hello.exe
+

hello.c

@@ -0,0 +1,7 @@
+#define __USE_MINGW_ANSI_STDIO 1
+#include <stdio.h>
+
+int main(int argc, char* argv[]) {
+	printf("hello world! %f\n", 42.0);
+	return 0;
+}