Fix module export to respect ed25519 flag (#210)

Author: DmitriyMusatkin

cmake/aws-c-cal-config.cmake

@@ -2,8 +2,8 @@ include(CMakeFindDependencyMacro)
 
 find_dependency(aws-c-common)
 
-if (NOT @BYO_CRYPTO@ AND NOT WIN32 AND NOT APPLE) # if NOT BYO_CRYPTO AND NOT WIN32 AND NOT APPLE
-    if (@USE_OPENSSL@ AND NOT ANDROID) # if USE_OPENSSL AND NOT ANDROID
+if (NOT @BYO_CRYPTO@ AND (@AWS_USE_LIBCRYPTO_TO_SUPPORT_ED25519_EVERYWHERE@ OR (NOT WIN32 AND NOT APPLE)))
+    if (@USE_OPENSSL@ AND NOT ANDROID)
         # aws-c-cal has been built with a dependency on OpenSSL::Crypto,
         # therefore consumers of this library have a dependency on OpenSSL and must have it found
         find_dependency(OpenSSL REQUIRED)