make-release: don't rely on $CWD when excluding subproject directories

The current logic scans qemu.git/subprojects/ from *.wrap files to
determine whether or not to include the associated directories in the
release tarballs. However, the script assumes that it is being run from
the top-level of the source directory, which may not always be the case.
In particular, when generating releases via, e.g.:

  make qemu-9.2.1.tar.xz

the $CWD will either be an arbitrary external build directory, or
qemu.git/build, and the exclusions will not be processed as expected.
Fix this by using the $src parameter passed to the script as the root
directory for the various subproject/ paths referenced by this logic.

Also, the error case at the beginning of the subproject_dir() will not
result in the error message being printed, and will instead produce an
error message about "error" not being a valid command. Fix this by using
basic shell commands.

Fixes: be27b5149c86 ("make-release: only leave tarball of wrap-file subprojects")
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Michael Tokarev <mjt@tls.msk.ru>
Cc: qemu-stable@nongnu.org
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

scripts/make-release

@@ -11,8 +11,9 @@
 # See the COPYING file in the top-level directory.
 
 function subproject_dir() {
-    if test ! -f "subprojects/$1.wrap"; then
-      error "scripts/archive-source.sh should only process wrap subprojects"
+    if test ! -f "$src/subprojects/$1.wrap"; then
+      echo "scripts/archive-source.sh should only process wrap subprojects"
+      exit 1
     fi
 
     # Print the directory key of the wrap file, defaulting to the
@@ -26,7 +27,7 @@ function subproject_dir() {
       -e    's///p' \
       -e    'q' \
       -e '}' \
-      "subprojects/$1.wrap")
+      "$src/subprojects/$1.wrap")
 
     echo "${dir:-$1}"
 }
@@ -76,7 +77,7 @@ popd
 exclude=(--exclude=.git)
 # include the tarballs in subprojects/packagecache but not their expansion
 for sp in $SUBPROJECTS; do
-    if grep -xqF "[wrap-file]" subprojects/$sp.wrap; then
+    if grep -xqF "[wrap-file]" $src/subprojects/$sp.wrap; then
       exclude+=(--exclude=subprojects/"$(subproject_dir $sp)")
     fi
 done