added better reporting for yasm program+feature check

Author: embray

build/pkgs/yasm/spkg-configure.m4

@@ -2,8 +2,10 @@ SAGE_SPKG_CONFIGURE(
     [yasm],
     # Yasm is only needed on x86(_64) systems; check also for system yasm which
     # must support "adox" (new Skylake instruction)
-    [AC_PATH_PROGS_FEATURE_CHECK([YASM], [yasm],
+    [AC_MSG_CHECKING([for yasm supporting the adox instruction])
+     AC_PATH_PROGS_FEATURE_CHECK([YASM], [yasm],
         [[{ echo "BITS 64"; echo "adox rax, rax"; } | ${ac_path_YASM} - -o /dev/null >/dev/null 2>/dev/null && ac_cv_path_YASM=${ac_path_YASM}]],
-        [sage_spkg_install_yasm=yes; ac_cv_path_YASM=no])],
+        [sage_spkg_install_yasm=yes; ac_cv_path_YASM=no])
+     AC_MSG_RESULT($ac_cv_path_YASM)],
     [AS_CASE("$host_cpu", [i@<:@0-9@:>@86|x86_64], [sage_require_yasm=yes])]
 )