gstlal-burst: only call setrlimit on linux

it causes errors on macos with python3

gstlal-burst/bin/gstlal_snax_extract

@@ -72,16 +72,17 @@ def setrlimit(res, lim):
 	resource.setrlimit(res, (lim if lim is not None else hard_lim, hard_lim))
 
 
-# set the number of processes and total set size up to hard limit and
-# shrink the per-thread stack size (default is 10 MiB)
-setrlimit(resource.RLIMIT_NPROC, None)
-setrlimit(resource.RLIMIT_AS, None)
-setrlimit(resource.RLIMIT_RSS, None)
-
-# FIXME:  tests at CIT show that this next tweak has no effect.  it's
-# possible that SL7 has lowered the default stack size from SL6 and we
-# don't need to do this anymore.  remove?
-setrlimit(resource.RLIMIT_STACK, 1024 * 1024)  # 1 MiB per thread
+if sys.platform == "linux":
+	# set the number of processes and total set size up to hard limit and
+	# shrink the per-thread stack size (default is 10 MiB)
+	setrlimit(resource.RLIMIT_NPROC, None)
+	setrlimit(resource.RLIMIT_AS, None)
+	setrlimit(resource.RLIMIT_RSS, None)
+
+	# FIXME:  tests at CIT show that this next tweak has no effect.  it's
+	# possible that SL7 has lowered the default stack size from SL6 and we
+	# don't need to do this anymore.  remove?
+	setrlimit(resource.RLIMIT_STACK, 1024 * 1024)  # 1 MiB per thread
 
 
 # =============================