ci: freebsd: synthesize a bzip2.pc if the bzip2 package doesn't ship one

Installing bzip2 (previous commit) wasn't enough: on this CI image the
package provides libbz2 + headers but no bzip2.pc, so pkgconf's
dependency resolution for freetype2 (Requires.private: bzip2, pulled in
transitively by xfont2) still fails outright even though the library
itself is present and usable - confirmed via the job log still showing
'Package bzip2 was not found in the pkg-config search path' with
env[PKG_CONFIG_PATH] correctly unset (default search path), ruling out
a path problem. This is missing package metadata, not a missing
library: write a minimal bzip2.pc if pkg-config --exists bzip2 fails,
locating the actual installed lib/header paths via 'pkg info -l bzip2'
rather than hardcoding them.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>

.github/scripts/freebsd/install-pkg.sh

@@ -63,3 +63,36 @@ retry pkg install -y \
     xcb-util-wm \
     xkbcomp \
     xorgproto
+
+# The FreeBSD `bzip2` package installs libbz2 + headers but, at least on
+# this CI image, no bzip2.pc — freetype2's own .pc lists bzip2 in
+# Requires.private, so pkgconf's dependency resolution for xfont2 (which
+# needs freetype2) fails outright even though the actual library is
+# present and perfectly usable. This is a missing-metadata gap in the
+# package, not a missing library — synthesize the .pc pkgconf itself
+# never shipped, pointing at wherever `pkg` actually placed the files
+# (found via `pkg info -l`, not hardcoded, since the exact split between
+# base-system and /usr/local varies).
+if ! pkg-config --exists bzip2 2>/dev/null; then
+    echo "--> bzip2.pc missing from the bzip2 package; synthesizing one"
+    bz_hdr=$(pkg info -l bzip2 | grep -m1 '/bzlib\.h$') || true
+    bz_lib=$(pkg info -l bzip2 | grep -m1 '/libbz2\.so$') || true
+    bz_incdir=$(dirname "${bz_hdr:-/usr/local/include/bzlib.h}")
+    bz_libdir=$(dirname "${bz_lib:-/usr/local/lib/libbz2.so}")
+    bz_ver=$(pkg info bzip2 2>/dev/null | awk -F'[-:]' '/^Version/ {print $2; exit}')
+    pcdir=/usr/local/libdata/pkgconfig
+    mkdir -p "$pcdir"
+    cat > "$pcdir/bzip2.pc" <<EOF
+prefix=/usr/local
+libdir=$bz_libdir
+includedir=$bz_incdir
+
+Name: bzip2
+Description: bzip2 compression library
+Version: ${bz_ver:-1.0.8}
+Libs: -L\${libdir} -lbz2
+Cflags: -I\${includedir}
+EOF
+    echo "--> wrote $pcdir/bzip2.pc:"
+    cat "$pcdir/bzip2.pc"
+fi