Allow uname calls in download mode + Fix handling of files without RPATH

[BillyONeal]

... and don't fetch patchelf unless we actually need it. For example cmake helper ports have no need to fetch patchelf.

In #36056 , things were changed to unconditionally patchelf when targeting Linux. Unfortunately that broke --only-downloads a lot of the time. This fixes that.

Also contains @Osyotr 's fixes from #37190 to coalesce world rebuilds a bit, so repeating comments from there:

Fixes #37183
Towards #25668

[dg0yt]

Note that you must ensure that vcpkg_find_acquire_program(PATCHELF) is called in download mode in order to have it available in disconnected operation.

I wonder if the result of uname -m shouldn't be cached, early, for the current run. If not already known by the tool.

[Neumann-A]

Looking at the logs it seems like the REMOVE_DUPLICATES call needs to be later in the fixup script.

[Osyotr]

Looking at the logs it seems like the REMOVE_DUPLICATES call needs to be later in the fixup script.

It's harmless but would be nice to fix.
Adjusted RPATH of '/mnt/vcpkg-ci/p/hdf5_x64-linux/tools/hdf5/gif2h5-shared' (From '' -> To '$ORIGIN:$ORIGIN/../../lib:$ORIGIN/../../lib:$ORIGIN/../lib:$ORIGIN')

[BillyONeal]

It's harmless but would be nice to fix. Adjusted RPATH of '/mnt/vcpkg-ci/p/hdf5_x64-linux/tools/hdf5/gif2h5-shared' (From '' -> To '$ORIGIN:$ORIGIN/../../lib:$ORIGIN/../../lib:$ORIGIN/../lib:$ORIGIN')

I get $ORIGIN:$ORIGIN/../../lib but why $ORIGIN/../lib ?

[Neumann-A]

I get $ORIGIN:$ORIGIN/../../lib but why $ORIGIN/../lib ?

Unix structure. If you are in /bin you need ../lib. The real question here is how does it go from "" to 4 entries since only two should be added.

[BillyONeal]

Unix structure. If you are in /bin you need ../lib. The real question here is how does it go from "" to 4 entries since only two should be added.

Can you double check the test I added then since there's clearly something I'm misunderstanding here

[Neumann-A]

-- Adjusted RPATH of '/mnt/vcpkg-ci/p/llvm_x64-linux/debug/lib/LLVMPolly.so' (From '' -> To '$ORIGIN')
-- Adjusted RPATH of '/mnt/vcpkg-ci/p/llvm_x64-linux/debug/lib/libLTO.so.17' (From '' -> To '$ORIGIN:$ORIGIN/../lib')

I feel like there is some variable being reused between runs.

[Neumann-A]

Ah the message is wrong:
message(STATUS "Adjusted RPATH of '${elf_file}' (From '${org_rpath}' -> To '${new_rpath}')")
needs to be changed to:
message(STATUS "Adjusted RPATH of '${elf_file}' (From '${readelf_output}' -> To '${new_rpath}')")

the refactor broke it.

[BillyONeal]

Ah the message is wrong: message(STATUS "Adjusted RPATH of '${elf_file}' (From '${org_rpath}' -> To '${new_rpath}')") needs to be changed to: message(STATUS "Adjusted RPATH of '${elf_file}' (From '${readelf_output}' -> To '${new_rpath}')")

the refactor broke it.

Fixed!

[Neumann-A]

Adjusted RPATH of '/mnt/vcpkg-ci/p/hdf5_x64-linux/tools/hdf5/gif2h5' (From '/mnt/vcpkg-ci/installed/x64-linux/lib:$ORIGIN/../lib:$ORIGIN/' -> To '$ORIGIN:$ORIGIN/../../lib:$ORIGIN/../lib')

looks ok now. It is just keeping already existing rpath settings.

[BillyONeal]

The only Linux failure matched https://dev.azure.com/vcpkg/public/_build/results?buildId=100228&view=results