RISC-V: Fix testsuite regression caused by quotes around options.

	2019-03-18  Kito Cheng  <kito.cheng@gmail.com>
	* gcc.target/riscv/arch-1.c: Add quotes around march in dg-error.

From-SVN: r269779

gcc/testsuite/ChangeLog

+2019-03-18  Kito Cheng  <kito.cheng@gmail.com>
+
+	* gcc.target/riscv/arch-1.c: Add quotes around march in dg-error.
+
 2019-03-18  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	* gcc.target/powerpc/bswap16.c: Use a pointer instead of a global for

gcc/testsuite/gcc.target/riscv/arch-1.c

@@ -3,4 +3,4 @@
 int foo()
 {
 }
-/* { dg-error ".-march=rv32I: first ISA subset must be `e', `i' or `g'" "" { target *-*-* } 0 } */
+/* { dg-error ".'-march=rv32I': first ISA subset must be `e', `i' or `g'" "" { target *-*-* } 0 } */