Comment out the set -u (nounset) shell option in test-driver,
which errors out when encountering unset variables.
During "gmake test" the pcregrep binary is never called because it
causes a problem in the pcregrep libtool wrapper for
an unset variable $libtool_install_magic.
Problem is not seen when running "gmake check" directly from
command line.  Solaris-specific patch not appropriate for upstream.

--- pcre-8.37-orig/test-driver	2015-04-28 04:17:22.000000000 -0700
+++ pcre-8.37/test-driver	2015-06-19 11:43:59.905679371 -0700
@@ -29,7 +29,7 @@ scriptversion=2013-07-13.22; # UTC
 
 # Make unconditional expansion of undefined variables an error.  This
 # helps a lot in preventing typo-related bugs.
-set -u
+# set -u
 
 usage_error ()
 {