Update Zlib-ng.cmake

Author: flagarde

modules/Zlib-ng.cmake

@@ -60,7 +60,11 @@ if(COMPILE_ZLIB)
                  OPTIONS "${zlib-ng_OPTIONS}")
 
   if(zlib-ng_ADDED)
-    file(STRINGS "${zlib-ng_SOURCE_DIR}/zlib.h" ZLIB_H REGEX "^#define ZLIB_VERSION \"[^\"]*\"$")
+    if(EXISTS "${zlib-ng_SOURCE_DIR}/zlib.h.in")
+      file(STRINGS "${zlib-ng_SOURCE_DIR}/zlib.h.in" ZLIB_H REGEX "^#define ZLIB_VERSION \"[^\"]*\"$")
+    else()
+      file(STRINGS "${zlib-ng_SOURCE_DIR}/zlib.h" ZLIB_H REGEX "^#define ZLIB_VERSION \"[^\"]*\"$")
+    endif()
     string(REGEX REPLACE "^.*ZLIB_VERSION \"([0-9]+).*$" "\\1" ZLIB_VERSION_MAJOR "${ZLIB_H}")
     string(REGEX REPLACE "^.*ZLIB_VERSION \"[0-9]+\\.([0-9]+).*$" "\\1" ZLIB_VERSION_MINOR  "${ZLIB_H}")
     string(REGEX REPLACE "^.*ZLIB_VERSION \"[0-9]+\\.[0-9]+\\.([0-9]+).*$" "\\1" ZLIB_VERSION_PATCH "${ZLIB_H}")