elf: Don't use .set for alpha target

Since the .set directive of ELF/alpha target is different, define NO_SET
to 1 to use "=" for ELF/alpha target.

	* testsuite/ld-elf/elf.exp (ASFLAGS): Add "--defsym NO_SET=1" for
	alpha target.
	* testsuite/ld-elf/pr19789.s: Use "=" if NO_SET is defined.

ld/ChangeLog

@@ -1,3 +1,9 @@
+2020-04-18  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* testsuite/ld-elf/elf.exp (ASFLAGS): Add "--defsym NO_SET=1" for
+	alpha target.
+	* testsuite/ld-elf/pr19789.s: Use "=" if NO_SET is defined.
+
 2020-04-16  Stephen Casner  <casner@acm.org>
 
 	PR 18963

ld/testsuite/ld-elf/elf.exp

@@ -43,6 +43,7 @@ if { [istarget alpha*-*-* ] } {
     # executable down into the low address space to match.
     # ??? How can we adjust just the one testcase?
     set LDFLAGS "$LDFLAGS -Ttext-segment 0x1000000"
+    set ASFLAGS "$ASFLAGS --defsym NO_SET=1"
 }
 
 if { [istarget "*-*-nacl*"] } {

ld/testsuite/ld-elf/pr19789.s

@@ -4,6 +4,10 @@
 __foo:
 	.byte 0
 	.globl	__foo1
+	.ifdef NO_SET
+	__foo1 = __foo
+	.else
 	.set __foo1, __foo
+	.endif
 	.symver __foo,foo@@VERS.2
 	.symver __foo1,foo@VERS.1