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/nalu/package.py

@@ -39,7 +39,7 @@ class Nalu(CMakePackage):
             git='https://github.com/NaluCFD/Nalu.git', branch='master')
 
     # Currently Nalu only builds static libraries; To be fixed soon
-    depends_on('yaml-cpp+fpic~shared')
+    depends_on('yaml-cpp+pic~shared')
     depends_on('trilinos~shared+exodus+tpetra+muelu+belos+ifpack2+amesos2+zoltan+stk+boost~superlu-dist+superlu+hdf5+zlib+pnetcdf@master')
 
     def cmake_args(self):