testsuite, aarch64: Normalise options to aarch64.exp.

When the compiler is configured --with-cpu= and that is different from
the baselines assumed, we see excess tes fails (primarly in body code
scans which are necessarily sensitive to costs).  To stabilize the
testsuite against such changes, use aarch64-with-arch-dg-options ()
to provide suitable consistent defaults.

e.g. for --with-cpu=xgene1 we see over 100 excess fails which are
removed by this change.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/aarch64.exp: Use aarch64-with-arch-dg-options
	to normaize the options to the tests in aarch64.exp.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>

gcc/testsuite/gcc.target/aarch64/aarch64.exp

@@ -37,9 +37,10 @@ if ![info exists DEFAULT_CFLAGS] then {
 # Initialize `dg'.
 dg-init
 
-# Main loop.
-dg-runtest [lsort [glob -nocomplain $srcdir/$subdir/*.\[cCS\]]] \
-	"" $DEFAULT_CFLAGS
-
+aarch64-with-arch-dg-options "" {
+    # Main loop.
+    dg-runtest [lsort [glob -nocomplain $srcdir/$subdir/*.\[cCS\]]] \
+	    "" $DEFAULT_CFLAGS
+}
 # All done.
 dg-finish