We do nightly testing of our yocto layers against the latest kernel, uboot, trusted-firmware-a, and optee. On April 12th we started getting a build failure with trusted-firmware-a. I have tracked the issue down to this commit:

https://github.com/ARM-software/arm-trusted-firmware/commit/71c42e98bbe900ae...

Specifically, the line in make_helpers/utilities.mk:

escape-shell = '$(subst ',''',$(1))'

On the surface it feels like the ' is overused and might cause issues. I tried making the line:

escape-shell = $(subst ',''',$(1))

And the builds went back to working properly. Does that seem like a change that should be made, or was there a reason for the extra '' wrapper?

I have submitted a GitHub issue about this as well:

https://github.com/TrustedFirmware-A/trusted-firmware-a/issues/7