This addresses an issue introduced in D91559. We would invoke the
compiler with -Lpath/to/lib --sysroot=path/to/sysroot where both
locations contain libraries with the same name, but we expect linker
to pick up the library in path/to/lib since that version is more
specialized. This was the case before D91559 where the sysroot path
would be ignored, but after that change linker would now pick up the
library from the sysroot which resulted in unexpected behavior.
The sysroot path should always come after any user provided library
paths, followed by compiler runtime paths. We want for libraries in user
provided library paths to always take precedence over sysroot libraries.
This matches the behavior of other toolchains used with other targets.
Differential Revision: https://reviews.llvm.org/D102049
Currently, Baremetal toolchain requires user to pass a sysroot location
using a --sysroot flag. This is not very convenient for the user. It also
creates problem for toolchain vendors who don't have a fixed location to
put the sysroot bits.
Clang does provide 'DEFAULT_SYSROOT' which can be used by the toolchain
builder to provide the default location. But it does not work if toolchain
is targeting multiple targets e.g. arm-none-eabi/riscv64-unknown-elf which
clang is capable of doing.
This patch tries to solve this problem by providing a default location of
the toolchain if user does not explicitly provides --sysroot. The exact
location and name can be different but it should fulfill these conditions:
1. The sysroot path should have a target triple element so that multi-target
toolchain problem (as I described above) could be addressed.
2. The location should not be $TOP/$Triple as this is used by gcc generally
and will be a problem for installing both gcc and clang based toolchain at
the same location.
Reviewed By: jroelofs
Differential Revision: https://reviews.llvm.org/D92677
Petr Hosek