depend-cleanup.sh: rebuild strrchr.o on riscv64 if it came from strrchr.S

We have to switch back to the previous rule once the temporary
build fix has been replaced with a permanent fix.

PR:		295823
See also:	4996ebdb72
Reported by:	siva
MFC after:	1 week

tools/build/depend-cleanup.sh

@@ -342,7 +342,7 @@ fi
 
 if [ ${MACHINE} = riscv ]; then
 	# 20251031  df21a004be23  libc: scalar strrchr() in RISC-V assembly
-	clean_dep   lib/libc strrchr c
+	#clean_dep   lib/libc strrchr c
 
 	# 20251031  563efdd3bd5d  libc: scalar memchr() in RISC-V assembly
 	clean_dep   lib/libc memchr c
@@ -366,8 +366,11 @@ if [ ${MACHINE} = riscv ]; then
 	clean_dep   lib/libc bcopy c "libc.string.bcopy.c"
 	clean_dep   lib/libc bzero c "libc.string.bzero.c"
 
-	# 20260307  2a4e3112c811   libc/riscv64: temporarily disable strnlen() implementation until a fix is developed
+	# 20260307  2a4e3112c811  libc/riscv64: temporarily disable strnlen() implementation until a fix is developed
 	clean_dep   lib/libc strnlen S
+
+	# 20260607  4996ebdb7200  libc/riscv64: temporarily disable strrchr() implementation until a fix is developed
+	clean_dep   lib/libc strrchr S
 fi
 
 if [ ${MACHINE_ARCH} = "aarch64" ]; then