GCC: Add strip variant to reduce installation size (#4670)

* gcc: Add strip variant

* gcc: Fix strip variant description being too long

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

@@ -74,6 +74,9 @@ class Gcc(AutotoolsPackage):
     variant('piclibs',
             default=False,
             description='Build PIC versions of libgfortran.a and libstdc++.a')
+    variant('strip',
+            default=False,
+            description='Strip executables to reduce installation size')
 
     # https://gcc.gnu.org/install/prerequisites.html
     depends_on('gmp@4.3.2:')
@@ -246,6 +249,12 @@ def build_targets(self):
             return ['bootstrap']
         return []
 
+    @property
+    def install_targets(self):
+        if '+strip' in self.spec:
+            return ['install-strip']
+        return ['install']
+
     @property
     def spec_dir(self):
         # e.g. lib/gcc/x86_64-unknown-linux-gnu/4.9.2