Run coverage for the spack install command as well as spack test.

- Also don't run coverage on OSX.

share/spack/qa/run-unit-tests

@@ -40,12 +40,13 @@ cd "$SPACK_ROOT"
 source "$SPACK_ROOT/share/spack/setup-env.sh"
 spack compilers
 spack config get compilers
-spack install -v libdwarf
 
 # Run unit tests with code coverage
 if [[ "$TRAVIS_PYTHON_VERSION" == 2.7 ]]; then
+    coverage run bin/spack install -v libdwarf
     coverage run bin/spack test "$@"
     coverage combine
 else
+    spack install -v libdwarf
     spack test "$@"
 fi