fix: remove current directory prefix when running from execroot
fix: remove current directory prefix when running from execroot

Fixes a regression where $PWD was included in the MAIN variable when
FROM_EXECROOT is defined.

bazelbuild/rules_nodejs,alexeagle/rules_nodejs,alexeagle/rules_nodejs,bazelbuild/rules_nodejs,bazelbuild/rules_nodejs,bazelbuild/rules_nodejs,bazelbuild/rules_nodejs,alexeagle/rules_nodejs,alexeagle/rules_nodejs