Make `zig version` compliant with SemVer (#1113)

The git revision is build metadata and should be appended with a plus sign.

https://semver.org/#spec-item-10

CMakeLists.txt

@@ -30,7 +30,7 @@ if(GIT_EXE)
             message("WARNING: Tag does not match configured Zig version")
         endif()
     else()
-        set(ZIG_VERSION "${ZIG_VERSION_MAJOR}.${ZIG_VERSION_MINOR}.${ZIG_VERSION_PATCH}.${ZIG_GIT_REV}")
+        set(ZIG_VERSION "${ZIG_VERSION}+${ZIG_GIT_REV}")
     endif()
 endif()
 message("Configuring zig version ${ZIG_VERSION}")