Add commit hash to window title for nightly builds.

This also adds a flag for detecting nightly builds in the code.

Makefile

@@ -123,6 +123,15 @@ endif
 endif
 endif
 
+# Stuff for showing the git hash in the intro on nightly builds
+# From https://stackoverflow.com/questions/44038428/include-git-commit-hash-and-or-branch-name-in-c-c-source
+ifeq ($(shell git rev-parse --abbrev-ref HEAD),nightly)
+  $(info Hello Caldera!!! I'm here all week!)
+  GIT_HASH=`git rev-parse --short HEAD`
+  COMPILE_TIME=`date -u +'%Y-%m-%d %H:%M:%S UTC'`
+  VERSION_CFLAGS += -DNIGHTLY -DGIT_HASH="\"$(GIT_HASH)\"" -DCOMPILE_TIME="\"$(COMPILE_TIME)\""
+endif
+
 # Microcode
 
 ifeq ($(GRUCODE),f3dex) # Fast3DEX

src/pc/gfx/gfx_sdl2.c

@@ -156,13 +156,18 @@ static void gfx_sdl_init(void) {
     else if (gCLIOpts.FullScreen == 2)
         configWindow.fullscreen = false;
 
-    const char* window_title = 
+    const char window_title[96] = 
     #ifndef USE_GLES
     "Super Mario 64 PC port (OpenGL)";
     #else
     "Super Mario 64 PC port (OpenGL_ES2)";
     #endif
 
+    #ifdef NIGHTLY
+    strcat(window_title, " nightly ");
+    strcat(window_title, GIT_HASH);
+    #endif
+
     wnd = SDL_CreateWindow(
         window_title,
         configWindow.x, configWindow.y, configWindow.w, configWindow.h,