Alr with fails: zlib/trees.o: relocation R_X86_64_PC32 against symbol `_length_code'

This same error occurs when you try to alr build a project that actually uses aws, but the repro steps are easier than that; just create a new project with Alire and add aws as a dependency and you get this error:

aws_21.0.0_57fddf8f/.build/x86_64-linux-gnu/release/relocatable/obj/zlib/trees.o: relocation R_X86_64_PC32 against symbol `_length_code' can not be used when making a shared object; recompile with -fPIC

Reproduction steps:

• Create a new project alr init --bin hello_aws; cd hello_aws
• Add aws alr with aws

You get this error:

/home/tama/.config/alire/cache/dependencies/gnat_native_11.2.4_2f37a10b/bin/../lib/gcc/x86_64-pc-linux-gnu/11.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: /home/tama/code/ada/hello_aws/alire/cache/dependencies/aws_21.0.0_57fddf8f/.build/x86_64-linux-gnu/release/relocatable/obj/zlib/trees.o: warning: relocation against `_length_code' in read-only section `.text'
/home/tama/.config/alire/cache/dependencies/gnat_native_11.2.4_2f37a10b/bin/../lib/gcc/x86_64-pc-linux-gnu/11.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: /home/tama/code/ada/hello_aws/alire/cache/dependencies/aws_21.0.0_57fddf8f/.build/x86_64-linux-gnu/release/relocatable/obj/zlib/trees.o: relocation R_X86_64_PC32 against symbol `_length_code' can not be used when making a shared object; recompile with -fPIC
/home/tama/.config/alire/cache/dependencies/gnat_native_11.2.4_2f37a10b/bin/../lib/gcc/x86_64-pc-linux-gnu/11.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: final link failed: bad value
collect2: error: ld returned 1 exit status
gprlib: /home/tama/.config/alire/cache/dependencies/gnat_native_11.2.4_2f37a10b/bin/gcc execution error
gprbuild: could not build library for project zlib
make: *** [Makefile:184: build-native] Error 4
error: A post-fetch action failed, re-run with -vv -d for details

Googling gives lots of results of solutions to this problem in other C libraries, and the solution is to add -fPIC to dependencies from the bottom up. I'm not sure how to do that for AWS.

Reproduce the failure with alr init --bin hello_aws followed by alr with aws, then inspect the AWS dependency build path around zlib/trees.o and the Makefile:184 build-native target. Trace how gprbuild compiles zlib and verify that the dependency build completes without the relocation error.