tests: sysroot: add test for sysroot deduplication

If ${pc_sysrootdir} is expanded in another variable, then it
may be included twice.

Ref: https://github.com/pkgconf/pkgconf/issues/307
Signed-off-by: Ariadne Conill <ariadne@ariadne.space>

tests/sysroot.sh

@@ -7,6 +7,7 @@ tests_init \
 	variable \
 	do_not_eat_slash \
 	do_not_duplicate_sysroot_dir \
+	do_not_duplicate_sysroot_dir_variable \
 	uninstalled \
 	uninstalled_pkgconf1 \
 	uninstalled_fdo \
@@ -66,6 +67,15 @@ do_not_duplicate_sysroot_dir_body()
 		pkgconf --cflags sysroot-dir-4
 }
 
+do_not_duplicate_sysroot_dir_variable_body()
+{
+	export PKG_CONFIG_SYSROOT_DIR="/sysroot"
+	atf_check \
+		-o inline:"/sysroot//usr/share/test\n" \
+		pkgconf --with-path="${selfdir}/lib1" --variable=pkgdatadir \
+		explicit-sysroot
+}
+
 uninstalled_body()
 {
 	export PKG_CONFIG_PATH="${selfdir}/lib1"