[Bug libobjc/64051] broken exception model detection in libobjc's configure

["ossman at cendio dot se" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64051

--- Comment #3 from Pierre Ossman <ossman at cendio dot se> ---
libstdc++ compiles fine though, but the previous stage did indeed include a C++
compiler. But even with that requirement, it still seems a bit dangerous. What
if the previous compiler uses a different exception model? Or changes some
other of all the myriad of options that affect compiler behaviour?

First compiler (from RHEL 7):

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-redhat-linux/4.8.2/lto-wrapper
Target: x86_64-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla
--enable-bootstrap --enable-shared --enable-threads=posix
--enable-checking=release --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-gnu-unique-object
--enable-linker-build-id --with-linker-hash-style=gnu
--enable-languages=c,c++,objc,obj-c++,java,fortran,ada,go,lto --enable-plugin
--enable-initfini-array --disable-libgcj
--with-isl=/builddir/build/BUILD/gcc-4.8.2-20140120/obj-x86_64-redhat-linux/isl-install
--with-cloog=/builddir/build/BUILD/gcc-4.8.2-20140120/obj-x86_64-redhat-linux/cloog-install
--enable-gnu-indirect-function --with-tune=generic --with-arch_32=x86-64
--build=x86_64-redhat-linux
Thread model: posix
gcc version 4.8.2 20140120 (Red Hat 4.8.2-16) (GCC) 

Second compiler:

$ i686-pc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/opt/cendio-build/arch/armhf/usr/bootstrap/bin/i686-pc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/opt/cendio-build/arch/armhf/usr/bootstrap/libexec/gcc/i686-pc-linux-gnu/4.5.4/lto-wrapper
Target: i686-pc-linux-gnu
Configured with: ../configure
--prefix=/opt/cendio-build/arch/armhf/usr/bootstrap
--with-gmp=/opt/cendio-build/arch/armhf/usr/bootstrap
--with-mpfr=/opt/cendio-build/arch/armhf/usr/bootstrap
--with-mpc=/opt/cendio-build/arch/armhf/usr/bootstrap
--target=i686-pc-linux-gnu --with-sysroot=/opt/cendio-build/arch/armhf
--with-system-zlib --with-gnu-as --with-gnu-ld --disable-nls --disable-multilib
--disable-libmudflap --enable-shared --enable-threads=posix
--enable-languages=c,c++
Thread model: posix
gcc version 4.5.4 (GCC) 

Third compiler:

../configure --host=i686-pc-linux-gnu --prefix=/usr --bindir=/usr/bin
--sbindir=/usr/sbin --sysconfdir=/etc --datadir=/usr/share
--includedir=/usr/include --libdir=/usr/lib --libexecdir=/usr/libexec
--localstatedir=/var --sharedstatedir=/var/lib --mandir=/usr/share/man
--infodir=/usr/share/info --build=cross-unknown-linux-gnu
--with-build-sysroot=/opt/cendio-build/arch/osx32 --target=i686-pc-linux-gnu
--with-sysroot=/ --with-system-zlib --with-gnu-as --with-gnu-ld --disable-nls
--disable-multilib --disable-libmudflap --enable-shared --enable-threads=posix
--enable-languages=c,c++,objc