Fix Linux flaky test completely

Author: DougGregor

test/stdlib/symbol-visibility-linux.test-sh

@@ -286,6 +286,8 @@
 // RUN:             -e _ZSteqIcSt11char_traitsIcESaIcEEbRKNSt7__cxx1112basic_stringIT_T0_T1_EEPKS5_ \
 // RUN:             -e _ZStplIcSt11char_traitsIcESaIcEENSt7__cxx1112basic_stringIT_T0_T1_EEPKS5_RKS8_ \
 // RUN:             -e _ZN9__gnu_cxx32__throw_concurrence_unlock_errorEv \
+// RUN:             -e _ZStplIcSt11char_traitsIcESaIcEENSt7__cxx1112basic_stringIT_T0_T1_EEOS8_PKS5_ \
+// RUN:             -e _ZStplIcSt11char_traitsIcESaIcEENSt7__cxx1112basic_stringIT_T0_T1_EEPKS5_OS8_ \
 // RUN:             -e _ZNKSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE11_M_disjunctEPKc \
 // RUN:             -e _ZNKSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE11_M_is_localEv \
 // RUN:             -e _ZNKSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE12find_last_ofEPKcm \