gcc-5.2.0 fails to compile itself

[john.frankish@laposte.net]

> Using gcc-5.2.0 to compile itself on an i486 x86 system with glibc-2.22, I am unable > to get it to compile with any of the following: 
> 
> CC="gcc -msse2 -flto -fuse-linker-plugin -march=i486 -mtune=i686 -Os -pipe" 
> CXX="g++ -msse2 -flto -fuse-linker-plugin -march=i486 -mtune=i686 -Os -pipe" 
> ../gcc-5.2.0/configure --prefix=/usr/local --enable-languages=c,c++ --disable-
> multilib --disable-bootstrap --with-system-zlib --libexecdir=/usr/local/lib --enable-
> frame-pointer 
> 
> CC="gcc -march=i486 -mtune=i686 -Os -pipe" CXX="g++ -march=i486 -mtune=i686 -Os 
> -pipe" ../gcc-5.2.0/configure --prefix=/usr/local --enable-languages=c,c++ --disable-
> multilib --disable-bootstrap --with-system-zlib --libexecdir=/usr/local/lib --enable-
> frame-pointer 
> 
> CFLAGS="-march=i486 -mtune=i686 -Os -pipe" CXXFLAGS="-march=i486 -mtune=i686 -Os 
> -pipe" ../gcc-5.2.0/configure --prefix=/usr/local --enable-languages=c,c++ --disable-
> multilib --disable-bootstrap --with-system-zlib --libexecdir=/usr/local/lib --enable-
> frame-pointer 
> 
> ../gcc-5.2.0/configure --prefix=/usr/local --enable-languages=c,c++ --disable-
> multilib --disable-bootstrap --with-system-zlib --libexecdir=/usr/local/lib --enable-
> frame-pointer 
> 
> ..the latter was also tried and failed on an i686 x86 system. Oddly enough the errors > are different in each case. 
> 
> Note that all of the above work without error using gcc-4.9.1 and glibc-2.20. 
> 
> Since the errors are different in each case, it's not that obvious what the problem 
> might be? 
> 

Bump - can anybody help (detailed errors in first message)?