Changed every 'fpic' variant to 'pic' (#4969)

* Changed every 'fpic' variant to 'pic'. fixes #2463

Every variant that activates compilation of position independent code
has been changed to 'pic'. Hardcoded compiler flags in packages have
been substituted with `self.compiler.pic_flag`.

* Changed literal uses of '-fpic' to 'self.compiler.pic_flag'

var/spack/repos/builtin/packages/cantera/package.py

@@ -78,7 +78,7 @@ def install(self, spec, prefix):
             'CXX={0}'.format(os.environ['CXX']),
             'F77={0}'.format(os.environ['F77']),
             'FORTRAN={0}'.format(os.environ['FC']),
-            'cc_flags=-fPIC',
+            'cc_flags={0}'.format(self.compiler.pic_flag),
             # Allow Spack environment variables to propagate through to SCons
             'env_vars=all'
         ]