package/libmodsecurity: point to staging pcre-config

The libmodsecurity build system uses the file installed on the host if not
explicitly pointed to pcre-config in the staging dir.

Fixes:
- http://autobuild.buildroot.net/results/f936ad05bca4bb776917306700750ba6d2498ef0
  + similar failures for other architectures

Signed-off-by: Frank Vanbever <frank.vanbever@essensium.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/libmodsecurity/libmodsecurity.mk

@@ -18,6 +18,7 @@ LIBMODSECURITY_CONF_ENV = \
 
 LIBMODSECURITY_DEPENDENCIES = pcre
 LIBMODSECURITY_CONF_OPTS = \
+	--with-pcre="$(STAGING_DIR)/usr/bin/pcre-config" \
 	--disable-examples \
 	--without-lmdb \
 	--without-ssdeep \