NO-JIRA: Fix C flags on ruby binding
NO-JIRA: Fix C flags on ruby binding

-fvisibility=hidden flag was causing an obscure failure in release builds.

ssorj/qpid-proton,gemmellr/qpid-proton-j,gemmellr/qpid-proton,ChugR/qpid-proton,kgiusti/qpid-proton,alanconway/qpid-proton,gemmellr/qpid-proton,ssorj/qpid-proton,alanconway/qpid-proton,astitcher/qpid-proton,kgiusti/qpid-proton,astitcher/qpid-proton,apache/qpid-proton,ssorj/qpid-proton,gemmellr/qpid-proton,gemmellr/qpid-proton,gemmellr/qpid-proton-j,ChugR/qpid-proton,ChugR/qpid-proton,astitcher/qpid-proton,gemmellr/qpid-proton,ChugR/qpid-proton,apache/qpid-proton,astitcher/qpid-proton,kgiusti/qpid-proton,kgiusti/qpid-proton,apache/qpid-proton,alanconway/qpid-proton,ssorj/qpid-proton,ChugR/qpid-proton,gemmellr/qpid-proton,kgiusti/qpid-proton,astitcher/qpid-proton,apache/qpid-proton,alanconway/qpid-proton,alanconway/qpid-proton,astitcher/qpid-proton,ssorj/qpid-proton,kgiusti/qpid-proton,ssorj/qpid-proton,apache/qpid-proton,apache/qpid-proton,alanconway/qpid-proton,ChugR/qpid-proton