Set compiler flags in CI workflow

These are the compiler flags used by libtopotoolbox. SWT will need to
compile cleanly in order to be merged into libtopotoolbox, so we must
resolve any compiler errors and warnings before moving
forward. I have set the compiler to error on any warnings, which is
somewhat strict, but will help us catch issues early on.

We set the flags in the CI workflow, not in the Makefile, to allow
consumers of this package to choose the appropriate flags. This way
one can still develop SWT in the presence of compiler warnings, but
you won't be able to contribute PRs until the compiler warnings are
resolved and the PR checks pass.

Signed-off-by: William Kearney <william.kearney@uni-potsdam.de>

Author: wkearn

.github/workflows/ci.yaml

@@ -10,6 +10,6 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
       - name: Build SWT
-        run: make
+        run: CFLAGS="-Werror -Wall -Wextra -Wpedantic -Wno-unused-parameter" make
       - name: Run tests
-        run: make check          
+        run: make check