testsuite: effective_target_march_option: support checking for -march=*

	* lib/target-supports.exp (effective_target_march_option): New.

I see no (other) way to, depending on the absence of an option,
add an option for a specific target.

For gcc.dg/torture/pr26515.c and cris-elf, you get an error for
supplying multiple (different) -march=... options (where that
error is desirable), like testing cris-elf with
RUNTESTFLAGS=--target_board=cris-sim/arch=v8, where otherwise
-march=v10 and -march=v8 will both be given, and the test would
fail.

For historians, this was accidentally misordered and committed after
the (first) patch using march_option.  Oops.

1 files changed, 4 insertions, 0 deletions

diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index 7916698..cdee31e 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -2477,6 +2477,10 @@ proc check_effective_target_ti_c64xp { } {
     }]
 }
 
+# Check if a -march=... option is given, as part of (earlier) options.
+proc check_effective_target_march_option { } {
+    return [check-flags [list "" { *-*-* } { "-march=*" } { "" } ]]
+}
 
 proc check_alpha_max_hw_available { } {
     return [check_runtime alpha_max_hw_available {