scons: Merge redundant checks for the socket library.

scons can accept more than one library at a time, so lets check for both
at once instead of writing out almost the same check twice.

Change-Id: I82f9bdf59a349e28ca75a615d711051256ec73a4
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/40869
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>

SConstruct

@@ -588,10 +588,9 @@ if main['USE_PYTHON']:
         warning('Python version too new. Python 3 expected.')
 
 # On Solaris you need to use libsocket for socket ops
-if not conf.CheckLibWithHeader(None, 'sys/socket.h', 'C++', 'accept(0,0,0);'):
-   if not conf.CheckLibWithHeader('socket', 'sys/socket.h',
-                                  'C++', 'accept(0,0,0);'):
-       error("Can't find library with socket calls (e.g. accept()).")
+if not conf.CheckLibWithHeader(
+        [None, 'socket'], 'sys/socket.h', 'C++', 'accept(0,0,0);'):
+   error("Can't find library with socket calls (e.g. accept()).")
 
 # Check for zlib.  If the check passes, libz will be automatically
 # added to the LIBS environment variable.