Properly deal with end of stream
diff --git a/Makefile b/Makefile
index 1465f36..9288909 100644
--- a/Makefile
+++ b/Makefile
@@ -189,11 +189,13 @@
 ZLIB_CHECK_CMD = $(CC) $(CFLAGS) $(CPPFLAGS) -o /dev/null test/build/zlib.c -lz $(LDFLAGS)
 PERFTOOLS_CHECK_CMD = $(CC) $(CFLAGS) $(CPPFLAGS) -o /dev/null test/build/perftools.c -lprofiler $(LDFLAGS)
 
+ifndef REQUIRE_CUSTOM_LIBRARIES_$(CONFIG)
 HAS_SYSTEM_PERFTOOLS = $(shell $(PERFTOOLS_CHECK_CMD) 2> /dev/null && echo true || echo false)
 ifeq ($(HAS_SYSTEM_PERFTOOLS),true)
 DEFINES += GRPC_HAVE_PERFTOOLS
 LIBS += profiler
 endif
+endif
 
 ifndef REQUIRE_CUSTOM_LIBRARIES_$(CONFIG)
 HAS_SYSTEM_OPENSSL_ALPN = $(shell $(OPENSSL_ALPN_CHECK_CMD) 2> /dev/null && echo true || echo false)