Escape @-sign in job template.

[nuclearsandwich]

Otherwise empy tries and fails to substitute the todays_date variable.

Follow-up to #424

Signed-off-by: Steven! Ragnarök steven@nuclearsandwich.com

[nuclearsandwich]

Example job diff

    <<<
    --- remote config
    +++ new config
    @@ -249,0 +250,3 @@
    +rem "Change dockerfile once per day to invalidate docker caches"
    +powershell "(Get-Content ${Env:DOCKERFILE}).replace('@todays_date', $(Get-Date).ToLongDateString()) | Set-Content ${Env:DOCKERFILE}"
    +
    @@ -253 +256 @@
    -set BUILD_ARGS=--build-arg WINDOWS_RELEASE_ID=%RELEASE_ID% --build-arg TODAYS_DATE="%date%"
    +set BUILD_ARGS=--build-arg WINDOWS_RELEASE_ID=%RELEASE_ID%
    >>>

[brawner]

This works, but we can also avoid using @ entirely so empy doesn't get the wrong idea (e.g. TODAYS_DATE)