[FIXUP] Make CC explicit and add missing CXX directive to regression tests.

Author: NlightNFotis

.github/workflows/pull-request-checks.yaml

@@ -77,23 +77,23 @@ jobs:
           cpanm Thread::Pool::Simple
       - name: Build with make
         run: |
-          make -C src       CXX='/usr/bin/clang++' -j2
-          make -C unit      CXX='/usr/bin/clang++' -j2
-          make -C jbmc/src  CXX='/usr/bin/clang++' -j2
-          make -C jbmc/unit CXX='/usr/bin/clang++' -j2
+          make -C src       CC='/usr/bin/clang' CXX='/usr/bin/clang++' -j2
+          make -C unit      CC='/usr/bin/clang' CXX='/usr/bin/clang++' -j2
+          make -C jbmc/src  CC='/usr/bin/clang' CXX='/usr/bin/clang++' -j2
+          make -C jbmc/unit CC='/usr/bin/clang' CXX='/usr/bin/clang++' -j2
       - name: Run unit tests
         run: |
-          make -C unit      CXX='/usr/bin/clang++' test
-          make -C jbmc/unit CXX='/usr/bin/clang++' test
+          make -C unit      CC='/usr/bin/clang' CXX='/usr/bin/clang++' test
+          make -C jbmc/unit CC='/usr/bin/clang' CXX='/usr/bin/clang++' test
           echo "Running expected failure tests"
-          make TAGS="[!shouldfail]" -C unit CXX='/usr/bin/clang++' test
-          make TAGS="[!shouldfail]" -C jbmc/unit CXX='/usr/bin/clang++' test
+          make TAGS="[!shouldfail]" -C unit CC='/usr/bin/clang' CXX='/usr/bin/clang++' test
+          make TAGS="[!shouldfail]" -C jbmc/unit CC='/usr/bin/clang' CXX='/usr/bin/clang++' test
       - name: Run regression tests
         run: |
-          make -C regression test-parallel JOBS=2
-          make -C regression/cbmc test-paths-lifo
+          make -C regression test-parallel CC='/usr/bin/clang' CXX='/usr/bin/clang++' JOBS=2
+          make -C regression/cbmc test-paths-lifo CC='/usr/bin/clang' CXX='/usr/bin/clang++'
           env PATH=$PATH:`pwd`/src/solvers make -C regression/cbmc test-cprover-smt2
-          make -C jbmc/regression test-parallel JOBS=2
+          make -C jbmc/regression test-parallel JOBS=2 CC='/usr/bin/clang' CXX='/usr/bin/clang++'
 
   check-ubuntu-20_04-cmake-gcc:
     runs-on: ubuntu-20.04