Fix up 'gcc.dg/pr78213.c' for '--enable-checking=release' etc.

Fix up 'gcc.dg/pr78213.c' for '--enable-checking=release' etc.

Fix up for r242748 (commit 3615816da830d41f67a5d8955ae588eba7f0b6fb)
"[PR target/78213] Do not ICE on non-empty -fself-test", as made
apparent by recent commit a42467bdb70650cd2f421e67b6c3418f74feaec2
"Restore 'gcc.dg/pr78213.c' testing", after the test case had gotten
disabled in r243681 (commit ecfc21ff34ddc6f8aa517251fb51494c68ff741f)
"Introduce selftest::locate_file" shortly after its original introduction.

	gcc/testsuite/
	PR testsuite/101969
	* gcc.dg/pr78213.c: Fix up for '--enable-checking=release' etc.