emacs: add 27.1 and conflict 26.3 on macos catalina (#18157)

* emacs: add version 27.1

* emacs: 26.3 does not work on macos catalina

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

@@ -14,6 +14,7 @@ class Emacs(AutotoolsPackage, GNUMirrorPackage):
     homepage = "https://www.gnu.org/software/emacs"
     gnu_mirror_path = "emacs/emacs-24.5.tar.gz"
 
+    version('27.1', sha256='ffbfa61dc951b92cf31ebe3efc86c5a9d4411a1222b8a4ae6716cfd0e2a584db')
     version('26.3', sha256='09c747e048137c99ed35747b012910b704e0974dde4db6696fde7054ce387591')
     version('26.2', sha256='4f99e52a38a737556932cc57479e85c305a37a8038aaceb5156625caf102b4eb')
     version('26.1', sha256='760382d5e8cdc5d0d079e8f754bce1136fbe1473be24bb885669b0e38fc56aa3')
@@ -47,6 +48,8 @@ class Emacs(AutotoolsPackage, GNUMirrorPackage):
     depends_on('gnutls', when='+tls')
     depends_on('jpeg')
 
+    conflicts('@:26.3', when='platform=darwin os=catalina')
+
     @when('platform=darwin')
     def setup_build_environment(self, env):
         # on macOS, emacs' config does search hard enough for ncurses'