Add version constraint to graphviz patches (#14377)

* Add version contraint to graphviz patches

This PR restricts the graphviz version that the patches for building
with the Intel compiler apply to. The two patches that were needed for
building graphviz-2.40.1 with the Intel compiler are not needed for
graphviz-2.42.2.

* Adjust the qt dependencies

The qt5 patch is only needed for graphviz-2.40.1. However, that version
will only compile with GCC-6 or greater.

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

@@ -24,6 +24,11 @@ class Graphviz(AutotoolsPackage):
     # This commit hash is tag='stable_release_2.40.1'
     version('2.40.1', commit='67cd2e5121379a38e0801cc05cce5033f8a2a609')
 
+    conflicts('%gcc@:5.9',
+              when='@2.40.1+qt ^qt@5:',
+              msg='graphviz-2.40.1 needs gcc-6 or greater to compile with QT5 '
+              'suppport')
+
     # Language bindings
     language_bindings = ['java']
 
@@ -59,14 +64,14 @@ class Graphviz(AutotoolsPackage):
 
     patch('http://www.linuxfromscratch.org/patches/blfs/9.0/graphviz-2.40.1-qt5-1.patch',
           sha256='bd532df325df811713e311d17aaeac3f5d6075ea4fd0eae8d989391e6afba930',
-          when='+qt^qt@5:')
+          when='@:2.40+qt^qt@5:')
     patch('https://raw.githubusercontent.com/easybuilders/easybuild-easyconfigs/master/easybuild/easyconfigs/g/Graphviz/Graphviz-2.38.0_icc_sfio.patch',
           sha256='393a0a772315a89dcc970b5efd4765d22dba83493d7956303673eb89c45b949f',
           level=0,
-          when='%intel')
+          when='@:2.40%intel')
     patch('https://raw.githubusercontent.com/easybuilders/easybuild-easyconfigs/master/easybuild/easyconfigs/g/Graphviz/Graphviz-2.40.1_icc_vmalloc.patch',
           sha256='813e6529e79161a18b0f24a969b7de22f8417b2e942239e658b5402884541bc2',
-          when='%intel')
+          when='@:2.40%intel')
 
     if not MACOS_VERSION:
         conflicts('+quartz',
@@ -95,7 +100,7 @@ class Graphviz(AutotoolsPackage):
     depends_on('libpng', when='+pangocairo')
     depends_on('pango', when='+pangocairo')
     depends_on('zlib')
-    depends_on('qt@4', when='+qt')
+    depends_on('qt', when='+qt')
     depends_on('libx11', when="+x")
 
     # Build dependencies