fix(glibc): +brewing strip — detect linker scripts without file(1)

Commit 6d105d8 added the +brewing strip but used `file(1)` to detect
linker-script-vs-ELF — and `file` isn't on the test-sandbox PATH
(it's its own package, not coreutils). Result: the type check raised
"file: command not found", the conditional fell through, no .so files
were sed'd, and the test still hit the +brewing linker error.

Detect linker scripts by their first-16-bytes marker `/* GNU ld script`
instead. That's a pure bash + grep + head check, all in the sandbox.

Also adds an echo so future CI logs make it obvious which files were
modified.

Author: tannevaled

projects/gnu.org/glibc/package.yml

@@ -130,15 +130,19 @@ build:
 
     # brewkit's fix-elf rewrites +brewing in ELF RPATH/RUNPATH, and
     # fix-shebangs.ts handles shell scripts. glibc additionally installs
-    # libc.so, libpthread.so, etc. as TEXT linker scripts (GROUP (...))
-    # that reference the install prefix by absolute path. Those need
-    # the same treatment, otherwise downstream `-lc` link attempts hit
-    # "cannot find +brewing/lib/glibc-X.Y/libc.so.6" because the
-    # +brewing suffix is gone from the final install dir.
+    # libc.so, libm.so, etc. as TEXT linker scripts (GROUP (...)) that
+    # reference the install prefix by absolute path. Those need the
+    # same treatment, otherwise downstream `-lc` link attempts hit
+    # "cannot find +brewing/lib/glibc-X.Y/libc.so.6" once brewkit
+    # renames the install dir to drop the +brewing suffix.
+    #
+    # We identify the scripts by their first-line marker rather than
+    # `file(1)` (not on the test-sandbox PATH).
     - run: |
         for f in $(find . -maxdepth 2 -type f -name '*.so'); do
-          if file "$f" | grep -qE 'ASCII text|GNU ld script'; then
+          if head -c 16 "$f" | grep -q "GNU ld script"; then
             sed -i 's|+brewing||g' "$f"
+            echo "stripped +brewing from $f"
           fi
         done
       working-directory: ${{prefix}}/lib