Build from source failure on linuxes with kernels older than 2.6.31

I'm trying to build QT5.1 on a Centos5 x86-64 that has a 2.6.18 kernel.
The build from source fails on qtbase/src/testlib/qbenchmarkperfevents.cpp because the code inside makes a syscall to check if SYS_perf_event_open is available on the platform. But as i have an older linux kernel, the symbol SYS_perf_event_open is not in my kernel headers, so the test function can't compile.
I think configure should check if this symbol is defined, and

• either add config macros that disable that functionality (comment the syscalls and make QBenchmarkPerfEventMeasurer::isAvailable() return 0)
• or display a configure error