Linker error while building on macOS

[skhaz]

ld: cannot link directly with dylib/framework, your binary is not an allowed client of /usr/lib/libcrypto.dylib for architecture x86_64

[syohex]

I'm not sure this is CMake issue or macOS issue or homebrew issue. CMake sets OPENSSL_LIBRARIES is "/usr/lib/libssl.dylib /usr/lib/libcrypto.dylib" even if OPENSSL_ROOT_DIR is set. (While OPENSSL_INCLUDE_DIR is set ${OPENSSL_ROOT_DIR}/include as expected)

I fixed this issue on my macOS catalina machine(Xcode11.4, cmake 3.17.2) with below patch.

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3c25dba..6efca4a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -95,6 +95,11 @@ SET(TEST_EXES test-minicrypto.t)
 
 FIND_PACKAGE(OpenSSL)
 IF (OPENSSL_FOUND AND NOT (OPENSSL_VERSION VERSION_LESS "1.0.1"))
+    IF (APPLE)
+      IF (DEFINED ${OPENSSL_ROOT_DIR})
+        LINK_DIRECTORIES(${OPENSSL_ROOT_DIR}/lib)
+      ENDIF()
+    ENDIF()
     MESSAGE(STATUS "  Enabling OpenSSL support")
     INCLUDE_DIRECTORIES(${OPENSSL_INCLUDE_DIR})
     ADD_LIBRARY(picotls-openssl lib/openssl.c)