Adds _dev_compile_options.dm to gitignore (#90950)

## About The Pull Request
Title.
## Why It's Good For The Game
Slightly less annoying testing

.gitignore

@@ -2,6 +2,7 @@
 
 # Local overrides--you can use this to change the config for your dev environment (like setting up SQL) without worrying about committing it
 /config/dev_overrides.txt
+/code/_dev_compile_options.dm
 
 #Ignore everything in datafolder and subdirectories
 /data/**/*

code/_dev_compile_options.dm

@@ -0,0 +1,4 @@
+// You can add here compile options without worrying about committing them.
+
+
+// #define TESTING

tgstation.dme

@@ -22,6 +22,7 @@
 #include "_maps\_basemap.dm"
 #include "code\__byond_version_compat.dm"
 #include "code\_compile_options.dm"
+#include "code\_dev_compile_options.dm"
 #include "code\_experiments.dm"
 #include "code\world.dm"
 #include "code\__DEFINES\__globals.dm"