Set environment variable for OpenSSL in CMake file (facebookincubator…

…#5309)

Summary:
Folly needs OpenSSL 1.1 version to function. In the presence of other
OpenSSL versions, it is possible that folly in bundled mode can pick up
other incompatible versions causing the build to fail.

Currently, in the `setup-macos.sh` script, we set
OPENSSL_ROOT_DIR=$(brew --prefix [email protected]).

We require a similar change for the bundled folly installs as well.
To achieve this goal, we now set the `OPENSSL_ROOT_DIR` environment
variable via the CMake file to set the path to the correct version of
OpenSSL.

Resolves facebookincubator#1446, facebookincubator#5309

CMakeLists.txt

@@ -247,6 +247,14 @@ set(CMAKE_POSITION_INDEPENDENT_CODE TRUE)
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED True)
 
+# Required so cmake can use the correct version of the OpenSSL dependency
+execute_process (
+        COMMAND brew --prefix [email protected]
+        OUTPUT_VARIABLE OPENSSL_ROOT_DIR
+        OUTPUT_STRIP_TRAILING_WHITESPACE
+)
+set(ENV{OPENSSL_ROOT_DIR} ${OPENSSL_ROOT_DIR})
+
 execute_process(
   COMMAND
     bash -c