build: remove BSD-specific /usr/local include path additions

It seems it's generally cleaner to leave this stuff to the BSDs.
Additionally, the NetBSD part wasn't even correct, because it made the
compiler prefer the system include path before local include files.

wscript

@@ -813,14 +813,6 @@ def configure(ctx):
     ctx.load('detections.compiler')
     ctx.load('detections.devices')
 
-    if ctx.env.DEST_OS in ('freebsd', 'openbsd'):
-        ctx.env.CFLAGS += ['-I.', '-I..', '-I/usr/local/include']
-        ctx.env.LINKFLAGS += ['-L/usr/local/lib']
-
-    if ctx.env.DEST_OS == 'netbsd':
-        ctx.env.CFLAGS += ['-I/usr/pkg/include']
-        ctx.env.LINKFLAGS += ['-L/usr/pkg/lib']
-
     ctx.parse_dependencies(build_options)
     ctx.parse_dependencies(main_dependencies)
     ctx.parse_dependencies(audio_output_features)