ci: Don't carry static libraries around for tests

Our current install tarball is 120ish MB zstd, and over 500MB unpacked.
A lot of this size was two static libraries which we'll obviously never
use at runtime.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31735>

.gitlab-ci/prepare-artifacts.sh

@@ -11,6 +11,7 @@ CROSS_FILE=/cross_file-"$CROSS".txt
 
 # Delete unused bin and includes from artifacts to save space.
 rm -rf install/bin install/include
+rm -f install/lib/*.a
 
 # Strip the drivers in the artifacts to cut 80% of the artifacts size.
 if [ -n "$CROSS" ]; then