build: Add library-based absl detection as a fallback

This should help for cases where users can make abseil-cpp available but
wiring up the CMake-build isn't that easy (for example, while
cross-compiling).
7 jobs for build-fixes in 38 seconds
Status Job ID Name Coverage
  Container
failed #10975506
aarch64
build-container-aarch64

00:00:08

passed #10498561
build-container-x86_64

00:00:30

failed #10498562
aarch64
build-container-aarch64

00:00:08

failed #10946067
aarch64
build-container-aarch64

00:00:10

failed #10498934
aarch64
build-container-aarch64

00:00:08

 
  Build
skipped #10498564
aarch64
build-aarch64
skipped #10498563
build-x86_64
 
Name Stage Failure
failed
build-container-aarch64 Container
$ if [[ -z "$CI_REGISTRY_IMAGE" ]] # collapsed multi-line command
/bin/sh: eval: line 136: podman: not found
$ podman login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
Uploading artifacts for failed job
Uploading artifacts...
WARNING: container-build-report.xml: no matching files
ERROR: No files to upload
Cleaning up file based variables
ERROR: Job failed: exit code 127