./configure doesn't understand Gentoo's build/host/target

Apparently there are several styles in how to write your build/host/target variables.

In Gentoo they look like this for my amd64 x86_64-pc-linux-gnu which doesn't play well with the current build system.

Default ./configure execution in Gentoo ebuilds will pass the following flags:

./configure --prefix=/usr --host=x86_64-pc-linux-gnu --mandir=/usr/share/man \
    --infodir=/usr/share/info --datadir=/usr/share --sysconfdir=/etc \
    --localstatedir=/var/lib --libdir=/usr/lib64 --build=x86_64-pc-linux-gnu

Which results in:

checking for gfind... no
checking for find... /usr/bin/find
checking for sort... /usr/bin/sort
checking for GHC version date... given 6.12.0.20091010
checking for ghc... /usr/bin/ghc
checking version of ghc... 6.10.4
Target platform inferred as: x86_64-unknown-linux
Unknown vendor linux

So we sed it like this:

build=`echo "$build" | sed -e 's/linux-gnu/linux/' -e 's/-pc-/-unknown-/'`
host=`echo "$host" | sed -e 's/linux-gnu/linux/' -e 's/-pc-/-unknown-/'`
target=`echo "$target" | sed -e 's/linux-gnu/linux/' -e 's/-pc-/-unknown-/'`

but of course we would prefer not to have to handle this specially.

That is, the vendor is pc and the OS is linux-gnu.

Trac metadata

Trac field	Value
Version	6.12.1 RC1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Build System
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture