rust coverage: remaps every rust subdirectory in fuzz

So that projects not using default fuzz_targets subdir
get the good remap, and hence the good coverage report

Author: catenacyber

infra/base-images/base-builder/cargo

@@ -35,7 +35,11 @@ then
     # go into fuzz directory if not already the case
     cd fuzz || true
     fuzz_src_abspath=`pwd`
-    export RUSTFLAGS="$RUSTFLAGS --remap-path-prefix fuzz_targets=$fuzz_src_abspath/fuzz_targets"
+    # Default directory is fuzz_targets, but some projects like image-rs use fuzzers.
+    while read i; do
+        export RUSTFLAGS="$RUSTFLAGS --remap-path-prefix $i=$fuzz_src_abspath/$i"
+        # Bash while syntax so that we modify RUSTFLAGS in main shell instead of a subshell.
+    done <<< "$(ls */*.rs | cut -d/ -f1 | uniq)"
     # we do not want to trigger debug assertions and stops
     export RUSTFLAGS="$RUSTFLAGS -C debug-assertions=no"
     # do not optimize with --release, leading to Malformed instrumentation profile data