/usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0/../../../x86_64-linux-gnu/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
/in/Compile/Makefile:44: recipe for target 'buildCalc' failed
make: *** [buildCalc] Error 1