csu: Add missing GNU-stack annotations to note object files.

ld.bfd marks the stack as executable for the crt objects due to the
missing annotations which raises a fatal warning starting with version
2.39.

lib/csu/common/crtbrand.S

@@ -47,3 +47,5 @@ __FBSDID("$FreeBSD$");
 2:	.p2align	2
 3:	.4byte		__FreeBSD_version
 4:
+
+	.section .note.GNU-stack,"",%progbits

lib/csu/common/feature_note.S

@@ -40,3 +40,5 @@ __FBSDID("$FreeBSD$");
 2:	.p2align	2
 3:	.4byte		0
 4:
+
+	.section .note.GNU-stack,"",%progbits

lib/csu/common/ignore_init_note.S

@@ -41,3 +41,5 @@ __FBSDID("$FreeBSD$");
 2:	.p2align	2
 3:	.4byte		0
 4:
+
+	.section .note.GNU-stack,"",%progbits