check: Add test for system flags pruning

Test that pkg-config respects the various environment variables that
override the system flags handling.

https://bugs.freedesktop.org/show_bug.cgi?id=94729

check/Makefile.am

@@ -30,6 +30,7 @@ TESTS = \
 	check-variable-override \
 	check-variables \
 	check-dependencies \
+	check-system-flags \
 	$(NULL)
 
 EXTRA_DIST = \
@@ -116,4 +117,5 @@ EXTRA_DIST = \
 	dependencies/i_dep_k_j.pc \
 	dependencies/j_dep_k.pc \
 	dependencies/k_dep.pc \
+	system.pc \
 	$(NULL)

check/check-system-flags

@@ -0,0 +1,47 @@
+#! /bin/sh
+
+set -e
+
+. ${srcdir}/common
+
+# Override the system paths in case pkg-config was built with something
+# that doesn't match the test pc file
+PKG_CONFIG_SYSTEM_INCLUDE_PATH=/usr/include
+if [ "$native_win32" = yes ]; then
+    PKG_CONFIG_SYSTEM_LIBRARY_PATH="/usr/lib;/lib"
+else
+    PKG_CONFIG_SYSTEM_LIBRARY_PATH=/usr/lib:/lib
+fi
+export PKG_CONFIG_SYSTEM_INCLUDE_PATH PKG_CONFIG_SYSTEM_LIBRARY_PATH
+
+RESULT=""
+run_test --cflags system
+
+RESULT="-lsystem"
+run_test --libs system
+
+# Make sure that the full paths come out when the *_ALLOW_SYSTEM_*
+# variables are set
+RESULT="-I/usr/include"
+PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=1 run_test --cflags system
+
+RESULT="-L/usr/lib -lsystem"
+PKG_CONFIG_ALLOW_SYSTEM_LIBS=1 run_test --libs system
+
+# Set the system paths to something else and test that the output
+# contains the full paths
+PKG_CONFIG_SYSTEM_INCLUDE_PATH=/foo/include
+PKG_CONFIG_SYSTEM_LIBRARY_PATH=/foo/lib
+
+RESULT="-I/usr/include"
+run_test --cflags system
+
+RESULT="-L/usr/lib -lsystem"
+run_test --libs system
+
+# Now check that the various compiler environment variables also update
+# the system include path
+for var in CPATH C_INCLUDE_PATH CPP_INCLUDE_PATH; do
+    RESULT=""
+    eval $var=/usr/include run_test --cflags system
+done

check/system.pc

@@ -0,0 +1,10 @@
+prefix=/usr
+exec_prefix=${prefix}
+libdir=${exec_prefix}/lib
+includedir=${prefix}/include
+
+Name: System library
+Description: Test package
+Version: 1.0.0
+Libs: -L${libdir} -lsystem
+Cflags: -I${includedir}