Update README.md cmake args

[etheory]

cmake does not allow a -SMTG_CREATE_PLUGIN_LINK=0 argument as outlined in the docs, the correct syntax would be: -DSMTG_CREATE_PLUGIN_LINK=0, same for -SMTG_PLUGIN_TARGET_USER_PROGRAM_FILES_COMMON=1 which should be -DSMTG_PLUGIN_TARGET_USER_PROGRAM_FILES_COMMON=1.

[ygrabit]

Thanks, will be fixed in next update