scons: put targets in global SConscript (#1180)

* Revert "remove unused scons argument (#1169)"

This reverts commit 702e5281d8.

* try this

* clean up

* default true

* default true

* already built

SConscript

@@ -0,0 +1,6 @@
+# panda fw
+SConscript('board/SConscript')
+
+# test files
+if GetOption('test'):
+  SConscript('tests/libpanda/SConscript')

SConstruct

@@ -1,5 +1,7 @@
-# panda fw
-SConscript('board/SConscript')
+AddOption('--test',
+          action='store_true',
+          default=True,
+          help='build test files')
 
-# test files
-SConscript('tests/libpanda/SConscript')
+# panda fw & test files
+SConscript('SConscript')

tests/libpanda/SConscript

@@ -5,7 +5,7 @@ env = Environment(
     '-fno-builtin',
     '-std=gnu11',
   ],
-  CPPPATH=[".", "#board/"],
+  CPPPATH=[".", "../../board"],
 )
 
 env.SharedLibrary("libpanda.so", ["safety_helpers.c"])

tests/safety/SConscript

@@ -1,11 +0,0 @@
-env = Environment(
-  CC='gcc',
-  CFLAGS=[
-    '-nostdlib',
-    '-fno-builtin',
-    '-std=gnu11',
-  ],
-  CPPPATH=[".", "../../board"],
-)
-
-env.SharedLibrary("libpandasafety.so", ["test.c"])