Compile issue with Cygwin

Compiling the referenced version of brotli did not succeed on Cygwin. I used the following workaround:

diff --git a/enc/Makefile b/enc/Makefile
index 7408d8a..1cf8b52 100644
--- a/enc/Makefile
+++ b/enc/Makefile
@@ -2,6 +2,12 @@

include ../shared.mk

+OSO := $(shell uname -o)
+
+ifeq ($(OSO), Cygwin)
- ```
CXXFLAGS += -include cstdlib
```

+endif
+

OBJS = backward_references.o block_splitter.o brotli_bit_stream.o encode.o encode_parallel.o entropy_encode.o histogram.o literal_cost.o metablock.o static_dict.o streams.o

all : $(OBJS)