Set version date to commit date instead of build date

Fixes #2688

This commit updates `build_odin.sh` and `build.bat` so that date of the commit
is used for the version tag, instead of the build time.

build.bat

@@ -51,7 +51,10 @@ set compiler_flags= -nologo -Oi -TP -fp:precise -Gm- -MP -FC -EHsc- -GR- -GF
 set compiler_defines= -DODIN_VERSION_RAW=\"%odin_version_raw%\"
 
 if not exist .git\ goto skip_git_hash
-for /f %%i in ('git rev-parse --short HEAD') do set GIT_SHA=%%i
+for /f "tokens=1,2" %%i IN ('git show "--pretty=%%cd %%h" "--date=format:%%Y-%%m" --no-patch --no-notes HEAD') do (
+	set odin_version_raw=%%i
+	set GIT_SHA=%%j
+)
 if %ERRORLEVEL% equ 0 set compiler_defines=%compiler_defines% -DGIT_SHA=\"%GIT_SHA%\"
 :skip_git_hash
 

build_odin.sh

@@ -8,17 +8,20 @@ set -eu
 : ${ODIN_VERSION=dev-$(date +"%Y-%m")}
 : ${GIT_SHA=}
 
-CPPFLAGS="$CPPFLAGS -DODIN_VERSION_RAW=\"$ODIN_VERSION\""
 CXXFLAGS="$CXXFLAGS -std=c++14"
 LDFLAGS="$LDFLAGS -pthread -lm -lstdc++"
 
-if [ -d ".git" ]; then
-	GIT_SHA=$(git rev-parse --short HEAD || :)
-	if [ "$GIT_SHA" ]; then
+if [ -d ".git" ] && [ $(which git) ]; then
+	versionTag=( $(git show --pretty='%cd %h' --date=format:%Y-%m --no-patch --no-notes HEAD) )
+	if [ $? -eq 0 ]; then
+		ODIN_VERSION="${versionTag[0]}"
+		GIT_SHA="${versionTag[1]}"
 		CPPFLAGS="$CPPFLAGS -DGIT_SHA=\"$GIT_SHA\""
 	fi
 fi
 
+CPPFLAGS="$CPPFLAGS -DODIN_VERSION_RAW=\"$ODIN_VERSION\""
+
 DISABLED_WARNINGS="-Wno-switch -Wno-macro-redefined -Wno-unused-value"
 OS=$(uname)