3105cfe783
Reland #82595 with fixes of build failures related to colored output. See https://lab.llvm.org/buildbot/#/builders/139/builds/60549 Use `%ProtectFileCheckOutput` to avoid colored output. Original commit message below. In `Pattern::parseVariable`, for global variables (those starting with '$') and for pseudo variables (those starting with '@') the first character is consumed before actual variable name parsing. If the name is empty, it leads to out-of-bound access to the corresponding `StringRef`. This patch adds an if statement against the case described.