`-fdump-ipa-inline` flag not supported by clang

```
FAILED: _deps/dotenv-cpp-build/CMakeFiles/tests.dir/Debug/tests/base_test.cc.o 
...
clang++: error: unknown argument: '-fdump-ipa-inline'
```

As the issue states I am using `clang`. This line introduced a breaking change in my build:

```
set(CMAKE_CXX_FLAGS_DEBUG "-g --coverage -fdump-ipa-inline")
```
I guess assuming `GCC`.