Cygwin testsuite failures - PCH?

[Billinghurst, David (CRTS)]

Recent mainline libstdc++-v3 tests on cygwin all fail with

libstdc++-v3/include/i686-pc-cygwin -I/usr/local/obj/gcc/i686-pc-cygwin/libstdc++-v3/include -I/usr/local/src/gcc/libstdc++-v3/libsupc++ -I/usr/local/src/gcc/libstdc++-v3/libio -I/usr/local/src/gcc/libstdc++-v3/include/backward -I/usr/local/src/gcc/libstdc++-v3/testsuite /usr/local/src/gcc/libstdc++-v3/testsuite/17_intro/header_cassert.cc -DDEBUG_ASSERT -L/usr/local/obj/gcc/i686-pc-cygwin/./libstdc++-v3/testsuite -lv3test -o ./header_cassert.exe  
<command line>:-82: sorry, unimplemented: had to relocate PCH 
<command line>:-82: internal compiler error: Segmentation fault Please submit a full bug report,

How can I turn off PCH for the testsuite until I get time to investigate?