Build bcu under Mac OS (M1 silicon)

[muddog]

If you failed to build bcu under Mac M1, then you probably meet OpenSSL version issue. Normally brew use OpenSSL@3 as default, but bcu requires 1.1. To fix this:

brew install openssl@1.1
export PKG_CONFIG_PATH=/opt/Cellar/openssl\@1.1/1.1.1q/lib/pkgconfig
export LIBOPENSSL_PREFIX=/opt/Cellar/openssl\@1.1/1.1.1q

Remove the libssh2 and curl executable boot from CMakelist of libcurl:

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5a1333397..c04e44264 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -73,7 +73,7 @@ include_directories(${CURL_SOURCE_DIR}/include)

 option(CURL_WERROR "Turn compiler warnings into errors" OFF)
 option(PICKY_COMPILER "Enable picky compiler options" ON)
-option(BUILD_CURL_EXE "Set to ON to build curl executable." ON)
+option(BUILD_CURL_EXE "Set to ON to build curl executable." OFF)
 option(BUILD_SHARED_LIBS "Build shared libraries" ON)
 option(ENABLE_ARES "Set to ON to enable c-ares support" OFF)
 if(WIN32)
@@ -639,7 +639,7 @@ if(CURL_BROTLI)
 endif()

 #libSSH2
-option(CMAKE_USE_LIBSSH2 "Use libSSH2" ON)
+option(CMAKE_USE_LIBSSH2 "Use libSSH2" OFF)
 mark_as_advanced(CMAKE_USE_LIBSSH2)
 set(USE_LIBSSH2 OFF)
 set(HAVE_LIBSSH2 OFF)

After that, do:

cmake .
./build_libs_mac.sh
make