config: fix CPU instruction set for cross-build

[ upstream commit d74543f8ad30db164c08ec69910b05d6811b1b89 ]

The platform value would be 'native' only when not cross build.
Move the operation about modifying cpu_instruction_set while
platform equals 'native' to the not cross build branch.

Fixes: bf66003 ("build: use platform for generic and native builds")

Signed-off-by: Joyce Kong <joyce.kong@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Tested-by: Pavan Nikhilesh <pbhagavatula@marvell.com>

config/meson.build

@@ -91,13 +91,14 @@ else
             cpu_instruction_set = 'generic'
         endif
     endif
+    if platform == 'native'
+        if cpu_instruction_set == 'auto'
+            cpu_instruction_set = 'native'
+        endif
+    endif
 endif
 
-if platform == 'native'
-    if cpu_instruction_set == 'auto'
-        cpu_instruction_set = 'native'
-    endif
-elif platform == 'generic'
+if platform == 'generic'
     if cpu_instruction_set == 'auto'
         cpu_instruction_set = 'generic'
     endif