Absolute path to the shell executable for Bazel to use. If this is unset, but the BAZEL_SH environment variable is set on the first Bazel invocation (that starts up a Bazel server), Bazel uses that. If neither is set, Bazel uses a hard-coded default path depending on the operating system it runs on (Windows: c:/msys64/usr/bin/bash.exe, FreeBSD: /usr/local/bin/bash, all others: /bin/bash). Note that using a shell that is not compatible with bash may lead to build failures or runtime failures of the generated binaries.