[PROTOBUF-3404] add --with-zlib=PATH to configure.ac script
diff --git a/configure.ac b/configure.ac
index 0d3e5fb..ae15f5f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -52,6 +52,16 @@
[include classes for streaming compressed data in and out @<:@default=check@:>@])],
[],[with_zlib=check])
+AC_ARG_WITH([zlib-include],
+ [AS_HELP_STRING([--with-zlib-include=PATH],
+ [zlib include directory])],
+ [CPPFLAGS="-I$withval $CPPFLAGS"])
+
+AC_ARG_WITH([zlib-lib],
+ [AS_HELP_STRING([--with-zlib-lib=PATH],
+ [zlib lib directory])],
+ [LDFLAGS="-L$withval $LDFLAGS"])
+
AC_ARG_WITH([protoc],
[AS_HELP_STRING([--with-protoc=COMMAND],
[use the given protoc command instead of building a new one when building tests (useful for cross-compiling)])],
