CMakeLists.txt: Do not use /usr as the default install location on MacOS.

Due to SIP(System Integrity Protection), libraries and other config files
can't be installed in this location.

Signed-off-by: Alexandra Trifan <Alexandra.Trifan@analog.com>

Author: AlexandraTrifan

CMakeLists.txt

@@ -14,7 +14,7 @@ if (WIN32)
 endif()
 
 # Set the default install path to /usr
-if (NOT WIN32 AND CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
+if (NOT APPLE AND NOT WIN32 AND CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
 	set(CMAKE_INSTALL_PREFIX "/usr" CACHE PATH "default install path" FORCE)
 endif()