tests: diff -r on Solaris emits "Common subdirectories:"

When using the -r option to Solaris diff, any directores that compare
identically are mentioned in the output.  We don't really care about these
directories for the purposes of this test, so ignore them.

tests/test-subrepo-deep-nested-change.t

@@ -172,7 +172,7 b' Test relative path printing + subrepos'
 Archive wdir() with subrepos
   $ hg rm main
   $ hg archive -S -r 'wdir()' ../wdir
-  $ diff -r . ../wdir | grep -v '\.hg$'
+  $ diff -r . ../wdir | egrep -v '\.hg$|^Common subdirectories:'
   Only in ../wdir: .hg_archival.txt
 
   $ find ../wdir -type f | sort
@@ -524,7 +524,7 b' largefile and a normal file. Then a lar'
   $ hg add sub1/sub2
 
   $ hg archive -S -r 'wdir()' ../wdir2
-  $ diff -r . ../wdir2 | grep -v '\.hg$'
+  $ diff -r . ../wdir2 | egrep -v '\.hg$|^Common subdirectories:'
   Only in ../wdir2: .hg_archival.txt
   Only in .: .hglf
   Only in .: foo
@@ -563,7 +563,7 b" Test 'wdir()' modified file archiving wi"
   $ echo 'mod' > large.bin
   $ echo 'mod' > sub1/sub2/large.dat
   $ hg archive -S -r 'wdir()' ../wdir3
-  $ diff -r . ../wdir3 | grep -v '\.hg$'
+  $ diff -r . ../wdir3 | egrep -v '\.hg$|^Common subdirectories'
   Only in ../wdir3: .hg_archival.txt
   Only in .: .hglf
   Only in .: foo