Use prebuilt aws-lc (#197)

CMakeLists.txt

@@ -101,10 +101,14 @@ else ()
         elseif(NOT USE_OPENSSL AND IN_SOURCE_BUILD)
             if (TARGET crypto)
                 message(STATUS "Using libcrypto from AWS-LC")
+                set(PLATFORM_LIBS crypto)
+            elseif(AWSLC_PREBUILT)
+                message(STATUS "Using prebuilt libcrypto from AWS-LC")
+                find_package(crypto REQUIRED)
+                set(PLATFORM_LIBS AWS::crypto)
             else()
                 message(FATAL_ERROR "Target crypto is not defined, failed to find libcrypto.")
             endif()
-            set(PLATFORM_LIBS crypto)
         else()
             #  note aws_use_package() does this for you, except it appends to the public link targets
             # which we probably don't want for this case where we want the crypto dependency private