scons,systemc: Drop the check for gcc version when building systemc.

The minimum version of gcc is 5, and the check would only fail if gcc
was older than that.

Change-Id: I20f4f42661baf415b7cbe80ec0ace4e427666348
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/41595
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>

src/systemc/SConsopts

@@ -25,17 +25,10 @@
 
 Import('*')
 
-from m5.util import compareVersions
-
 from gem5_scons import warning
 
 def use_systemc_check(env, warn=False):
-    if ('GCC_VERSION' in env and
-            compareVersions(env['GCC_VERSION'], '5.0') < 0):
-        if warn:
-            warning('Systemc may not work on gcc versions less than 5.0.')
-        return False
-    elif env['PLATFORM'] == 'darwin':
+    if env['PLATFORM'] == 'darwin':
         if warn:
             warning('Warning: Systemc may not work on Mac OS.')
         return False