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/zoltan/package.py

@@ -76,7 +76,7 @@ def install(self, spec, prefix):
         if '+shared' in spec:
             config_args.append('RANLIB=echo')
             config_args.append('--with-ar=$(CXX) -shared $(LDFLAGS) -o')
-            config_cflags.append('-fPIC')
+            config_cflags.append(self.compiler.pic_flag)
             if spec.satisfies('%gcc'):
                 config_args.append('--with-libs={0}'.format('-lgfortran'))