building ffmpeg testsuite on s390x with -O3 causes memory exhaustion

[Colin Watson]

cc1 allocates memory until it hits ENOMEM. The system has 8GiB of RAM and 6GiB of swap, and the source file is not very large or complex; the problem is not visible at -O2.

cc -I. -I./ -D_ISOC99_SOURCE -D_POSIX_C_SOURCE=200112 -D_XOPEN_SOURCE=600 -D_POSIX_C_SOURCE=200112 -D_XOPEN_SOURCE=600 -std=c99 -Wall -O3 -c -o tests/tiny_psnr.o tests/tiny_psnr.c -save-temps

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/s390x-linux-gnu/5/lto-wrapper
Target: s390x-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 5.3.1-3ubuntu1' --with-bugurl=file:///usr/share/doc/gcc-5/README.Bugs --enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-5 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-libitm --disable-libsanitizer --disable-libquadmath --enable-plugin --enable-default-pie --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-5-s390x/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-5-s390x --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-5-s390x --with-arch-directory=s390x --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch=zEC12 --with-long-double-128 --enable-multilib --enable-checking=release --build=s390x-linux-gnu --host=s390x-linux-gnu --target=s390x-linux-gnu
Thread model: posix
gcc version 5.3.1 20151207 (Ubuntu 5.3.1-3ubuntu1)