gcc: add v11.1.0 (#23294)

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

@@ -29,6 +29,8 @@ class Gcc(AutotoolsPackage, GNUMirrorPackage):
 
     version('master', branch='master')
 
+    version('11.1.0', sha256='4c4a6fb8a8396059241c2e674b85b351c26a5d678274007f076957afa1cc9ddf')
+
     version('10.3.0', sha256='64f404c1a650f27fc33da242e1f2df54952e3963a49e06e73f6940f3223ac344')
     version('10.2.0', sha256='b8dd4368bb9c7f0b98188317ee0254dd8cc99d1e3a18d0ff146c855fe16c1d8c')
     version('10.1.0', sha256='b6898a23844b656f1b68691c5c012036c2e694ac4b53a8918d4712ad876e7ea2')
@@ -125,7 +127,7 @@ class Gcc(AutotoolsPackage, GNUMirrorPackage):
     # GCC only tries to link with -lzstd but it requires
     # -pthread too when linking against libzstd.a, so
     # disable multithreading by default
-    depends_on('zstd ~multithread', when='@10:')
+    depends_on('zstd~multithread', when='@10:')
     depends_on('diffutils', type='build')
     depends_on('iconv', when='platform=darwin')
     depends_on('gnat', when='languages=ada')
@@ -226,6 +228,9 @@ class Gcc(AutotoolsPackage, GNUMirrorPackage):
     conflicts('~binutils', when='@7: os=rhel6',
               msg='New GCC cannot use system assembler on RHEL6')
 
+    # GCC 11 requires GCC 4.8 or later (https://gcc.gnu.org/gcc-11/changes.html)
+    conflicts('%gcc@:4.7', when='@11:')
+
     if sys.platform == 'darwin':
         # Fix parallel build on APFS filesystem
         # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81797