symbolize: use CROSS_COMPILE directive if available

Get CROSS_COMPILE prefix directive if defined in the environment.
If CROSS_COMPILE is not defined, default to aarch64-linux-gnu- or
arm-linux-gnueabihf- as done prior this change according to the
architecture read from the ELF file.

Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
diff --git a/scripts/symbolize.py b/scripts/symbolize.py
index aad7c2d..f7806c0 100755
--- a/scripts/symbolize.py
+++ b/scripts/symbolize.py
@@ -104,6 +104,9 @@
     def set_arch(self):
         if self._arch:
             return
+        self._arch = os.getenv('CROSS_COMPILE');
+        if self._arch:
+            return
         elf = self.get_elf(self._elfs[0][0])
         if elf is None:
             return