tests: add a test for pkg-config files

Add a test that does some basic validation of the pkg-config files.

Note: this is a port of Mbed-TLS#8988
but is moved into a different test component so cmake shared
infrastucture isn't needed.

Note this port of the patch detects the OS and skips so things like
freebsd do not fail.

Example run:
./tests/scripts/all.sh test_cmake_shared
******************************************************************
* test_cmake_shared: build/test: cmake shared
* Wed May 29 18:41:19 UTC 2024
******************************************************************
cmake -DUSE_SHARED_MBEDTLS_LIBRARY=On .
make
<snip>
testing package config file: mbedtls ... passed
testing package config file: mbedx509 ... passed
testing package config file: mbedcrypto ... passed
make clean

Signed-off-by: Bill Roberts <bill.roberts@arm.com>

tests/scripts/all.sh

@@ -2989,11 +2989,17 @@ component_test_make_shared () {
 
 component_test_cmake_shared () {
     msg "build/test: cmake shared" # ~ 2min
+    root_dir="$(pwd)"
     cmake -DUSE_SHARED_MBEDTLS_LIBRARY=On .
     make
     ldd programs/util/strerror | grep libmbedcrypto
     make test
     programs/test/dlopen_demo.sh
+    if [[ "$OSTYPE" == linux* ]]; then
+        PKG_CONFIG_PATH="${root_dir}/pkgconfig" ${root_dir}/tests/scripts/pkgconfig.sh
+    else
+        printf "Detected non-linux system of \"$OSTYPE\", not running pkgconfig.sh tests\n"
+    fi
 }
 
 test_build_opt () {

tests/scripts/pkgconfig.sh

@@ -0,0 +1,37 @@
+#!/bin/sh
+#
+# Copyright The Mbed TLS Contributors
+# SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+#
+# Purpose
+#
+# Test pkgconfig files.
+#
+# For each of the build pkg-config files, .pc files, check that
+# they validate and do some basic sanity testing on the output,
+# i.e. that the strings are non-empty.
+#
+# NOTE: This requires the built pc files to be on the pkg-config
+# search path, this can be controlled with env variable
+# PKG_CONFIG_PATH. See man(1) pkg-config for details.
+#
+
+set -e -u
+
+# These are the EXPECTED package names. Renaming these could break
+# consumers of pkg-config, consider carefully.
+all_pcs="mbedtls mbedx509 mbedcrypto"
+
+for pc in $all_pcs; do
+    printf "testing package config file: ${pc} ... "
+    pkg-config --validate "${pc}"
+    version="$(pkg-config --modversion "${pc}")"
+    test -n "$version"
+    cflags="$(pkg-config --cflags "${pc}")"
+    test -n "$cflags"
+    libs="$(pkg-config --libs "${pc}")"
+    test -n "$libs"
+    printf "passed\n"
+done
+
+exit 0