[testsuite] Fix pr27463.sh on riscv64

On riscv64, I run into:
...
cc main.c unavailable-dwarf-piece-dw.S -o unavailable-dwarf-piece
unavailable-dwarf-piece-dw.S: Assembler messages:
unavailable-dwarf-piece-dw.S:24: Error: non-constant .uleb128 is not supported
  ...
make: *** [Makefile:100: unavailable-dwarf-piece] Error 1
...

Fix this similar to commit 53c0488 "[testsuite] Fix pr25109.sh on riscv64".

2021-03-17  Tom de Vries  <tdevries@suse.de>

	* Makefile (no-multifile-prop): Allow target rule to fail.

---
 Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 2f7c76a..2990567 100644
--- a/Makefile
+++ b/Makefile
@@ -96,11 +96,11 @@ $(TEMP_ASM_FILES): %-dw.S: $(TEST_SRC)/../lib/%.exp
 	  export DEJAGNU=$(DEJAGNU); \
 	  runtest --tool=dwz -srcdir $(srcdir)/testsuite/ lib/$*.exp
 
-$(filter-out no-multifile-prop, $(TEST_EXECS_DWARF_ASM)): %: %-dw.S
+$(filter-out no-multifile-prop unavailable-dwarf-piece, $(TEST_EXECS_DWARF_ASM)): %: %-dw.S
 	$(CC) $(TEST_SRC)/main.c $< -o $@
 
 # Fails to compile on riscv64: Error: non-constant .uleb128 is not supported.
-no-multifile-prop: %: %-dw.S
+no-multifile-prop unavailable-dwarf-piece: %: %-dw.S
 	$(CC) $(TEST_SRC)/main.c $< -o $@ || true
 
 odr-struct: