Allow overriding pkg-config

Author: mtrojnar

configure.ac

@@ -26,9 +26,16 @@ ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 
 AC_CANONICAL_HOST
 AC_PROG_CC
-PKG_PROG_PKG_CONFIG
 AC_C_BIGENDIAN
 
+AC_ARG_WITH([pkg-config],
+	AS_HELP_STRING([--with-pkg-config=PATH],
+		[Specify the pkg-config program to use (default: pkg-config)]),
+	[PKG_CONFIG="$withval"],
+	[PKG_CONFIG="pkg-config"])
+AC_SUBST([PKG_CONFIG])
+PKG_PROG_PKG_CONFIG
+
 # we need to set our soversion based on openssl's soversion to avoid
 # issues with applications linking to new openssl, old libp11, and vice versa
 opensslversion="$( \