fix: use platform-appropriate shared lib extension for chez-ssl shim

ober

884dcd467e2c96ed0e0da4071e8fe67695be3275

diff --git a/Makefile b/Makefile
index 256396f..b8e9d6d 100644
--- a/Makefile
+++ b/Makefile
@@ -6,6 +6,13 @@ CHEZ = scheme
 SSL_DIR  ?= ../chez-ssl
 ZLIB_DIR ?= ../chez-zlib
 
+UNAME_S := $(shell uname -s)
+ifeq ($(UNAME_S),Darwin)
+  SO_EXT = .dylib
+else
+  SO_EXT = .so
+endif
+
 LIBDIRS = src:$(SSL_DIR)/src:$(ZLIB_DIR)/src
 
 .PHONY: all test test-unit clean deps
@@ -15,10 +22,10 @@ all:
 
 # Build chez-ssl shared object if not already built
 deps:
-	@test -f $(SSL_DIR)/chez_ssl_shim.so || $(MAKE) -C $(SSL_DIR)
+	@test -f $(SSL_DIR)/chez_ssl_shim$(SO_EXT) || $(MAKE) -C $(SSL_DIR)
 
 test: deps
-	@ln -sf $(realpath $(SSL_DIR))/chez_ssl_shim.so ./chez_ssl_shim.so
+	@ln -sf $(realpath $(SSL_DIR))/chez_ssl_shim$(SO_EXT) ./chez_ssl_shim$(SO_EXT)
 	$(CHEZ) --libdirs "$(LIBDIRS)" --script tests/https-test.ss
 
 clean: