Fix "test cases/common/131 generated assembly" on Solaris

Without this change, the test fails with:

[11/12] Linking target square-gen-test.
warning: Text relocation remains                referenced
    against symbol                  offset      in file
square_unsigned                     0x15        square-gen-test@exe/main.c.o
[12/12] Linking target square-ct-test.
warning: Text relocation remains                referenced
    against symbol                  offset      in file
square_unsigned                     0x15        square-ct-test@exe/main.c.o

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>

test cases/common/131 generated assembly/square-x86_64.S.in

@@ -19,7 +19,7 @@ END
 .text
 .globl SYMBOL_NAME(square_unsigned)
 /* Only supported with GAS */
-# if defined(__linux__) || defined(__DragonFly__) || defined(__FreeBSD__) || defined(__NetBSD__)
+# if defined(__linux__) || defined(__DragonFly__) || defined(__FreeBSD__) || defined(__NetBSD__) || defined(__sun)
 .type  square_unsigned,@function
 # endif