Fix build on "POSIX" systems

.github/workflows/ci.yml

@@ -8,7 +8,7 @@ jobs:
       - uses: actions/checkout@v1
       - name: build all and examples
         run: |
-          $(CC) -o ls ./examples/ls.c
+          $CC -o ls ./examples/ls.c
           ./ls
         env:
           CC: gcc
@@ -19,7 +19,7 @@ jobs:
       - uses: actions/checkout@v1
       - name: build all and examples
         run: |
-          $(CC) -o ls ./examples/ls.c
+          $CC -o ls ./examples/ls.c
           ./ls
         env:
           CC: clang
@@ -30,7 +30,7 @@ jobs:
       - uses: actions/checkout@v1
       - name: build all and examples
         run: |
-          $(CC) -o ls ./examples/ls.c
+          $CC -o ls ./examples/ls.c
           ./ls
         env:
           CC: clang