Merge pull request #4403 from hkleynhans/select_bundled_zlib

cmake: Allow user to select bundled zlib

CMakeLists.txt

@@ -55,6 +55,7 @@ OPTION( ENABLE_WERROR			"Enable compilation with -Werror"		OFF )
 IF (UNIX AND NOT APPLE)
 	OPTION( ENABLE_REPRODUCIBLE_BUILDS	"Enable reproducible builds" 			OFF )
 ENDIF()
+OPTION( USE_BUNDLED_ZLIB    "Use the bundled version of zlib"       OFF )
 
 IF(MSVC)
 	# This option is only available when building with MSVC. By default, libgit2

src/CMakeLists.txt

@@ -255,8 +255,9 @@ ELSE()
 ENDIF()
 
 # Optional external dependency: zlib
-FIND_PACKAGE(ZLIB)
-IF (ZLIB_FOUND)
+IF(NOT USE_BUNDLED_ZLIB)
+	FIND_PACKAGE(ZLIB)
+	IF(ZLIB_FOUND)
 		LIST(APPEND LIBGIT2_INCLUDES ${ZLIB_INCLUDE_DIRS})
 		LIST(APPEND LIBGIT2_LIBS ${ZLIB_LIBRARIES})
 		IF(APPLE OR CMAKE_SYSTEM_NAME MATCHES "FreeBSD")
@@ -265,13 +266,16 @@ IF (ZLIB_FOUND)
 		ELSE()
 			SET(LIBGIT2_PC_REQUIRES "${LIBGIT2_PC_REQUIRES} zlib")
 		ENDIF()
-	ADD_FEATURE_INFO(zlib ON "Zlib support")
-ELSE()
+		ADD_FEATURE_INFO(zlib ON "using system zlib")
+	ELSE()
 		MESSAGE(STATUS "zlib was not found; using bundled 3rd-party sources." )
+	ENDIF()
+ENDIF()
+IF(USE_BUNDLED_ZLIB OR NOT ZLIB_FOUND)
 	ADD_SUBDIRECTORY("${libgit2_SOURCE_DIR}/deps/zlib" "${libgit2_BINARY_DIR}/deps/zlib")
 	LIST(APPEND LIBGIT2_INCLUDES "${libgit2_SOURCE_DIR}/deps/zlib")
 	LIST(APPEND LIBGIT2_OBJECTS $<TARGET_OBJECTS:zlib>)
-	ADD_FEATURE_INFO(zlib ON "Zlib support (bundled)")
+	ADD_FEATURE_INFO(zlib ON "using bundled zlib")
 ENDIF()
 
 # Optional external dependency: libssh2