Change versioning system from `v0.13.1` to `dev-2021-04`

build.bat

@@ -1,5 +1,10 @@
 @echo off
 
+setlocal EnableDelayedExpansion
+
+set curr_year=%DATE:~-4%
+set curr_month=%DATE:~3,2%
+
 :: Make sure this is a decent name and not generic
 set exe_name=odin.exe
 
@@ -19,8 +24,11 @@ if "%2" == "1" (
     set nightly=0
 )
 
+set odin_version_raw="dev-%curr_year%-%curr_month%"
+
 set compiler_flags= -nologo -Oi -TP -fp:precise -Gm- -MP -FC -EHsc- -GR- -GF
 set compiler_defines=
+rem -DODIN_VERSION_RAW=%odin_version_raw%
 
 for /f %%i in ('git rev-parse --short HEAD') do set GIT_SHA=%%i
 if %ERRORLEVEL% equ 0 set compiler_defines=%compiler_defines% -DGIT_SHA=\"%GIT_SHA%\"

src/build_settings.cpp

@@ -71,9 +71,11 @@ TargetEndianKind target_endians[TargetArch_COUNT] = {
 	TargetEndian_Little,
 };
 
+#ifndef ODIN_VERSION_RAW
+#define ODIN_VERSION_RAW "dev-2021-unknown"
+#endif
 
-
-String const ODIN_VERSION = str_lit("0.13.1");
+String const ODIN_VERSION = str_lit(ODIN_VERSION_RAW);