gcc on FreeBSD/Gentoo/x86 has 'i686-gentoo-freebsd7.2' triplet, but ghc likes 'i386-unknown-freebsd'
Mangle -gentoo- to -unknown-, mangle '-freebsd7.2' (and other numerics) to '-freebsd'
Thanks to naota for the report and testing.
diff --git a/aclocal.m4 b/aclocal.m4
index f401860..7f93ebf 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -1333,7 +1333,7 @@ case "$1" in
 # converts vendor from gnu to ghc naming, and assigns the result to $target_var
 AC_DEFUN([GHC_CONVERT_VENDOR],[
 case "$1" in
-  pc)
+  pc|gentoo)
     $2="unknown"
     ;;
   *)
@@ -1354,6 +1354,10 @@ case "$1" in
   freebsd|netbsd|openbsd|dragonfly|osf1|osf3|hpux|linuxaout|kfreebsdgnu|freebsd2|solaris2|cygwin32|mingw32|darwin|gnu|nextstep2|nextstep3|sunos4|ultrix|irix|aix|haiku)
     $2="$1"
     ;;
+  # for things like freebsd7.2
+  freebsd*)
+    $2="freebsd"
+    ;;
   *)
     echo "Unknown OS $1"
     exit 1
diff --git a/configure.ac b/configure.ac
index 0360fa5..0a1ce25 100644
--- a/configure.ac
+++ b/configure.ac
@@ -225,7 +225,7 @@ then
                 echo "Bootstrapping GHC is a cross compiler. This probably isn't going to work"
         fi
 fi
-build=`echo "$build" | sed -e 's/linux-gnu/linux/' -e 's/-pc-/-unknown-/'`
+build=`echo "$build" | sed -e 's/linux-gnu/linux/' -e 's/-pc-/-unknown-/' -e 's/-gentoo-/-unknown-/' -e 's/freebsd.*$/freebsd/'`
 [build=`echo "$build" | sed -e 's/i[4-6]86/i386/'`] # escaping square bracket
 
 # We have to run these unconditionally, but we may discard their
@@ -260,7 +260,7 @@ else
     GHC_CONVERT_VENDOR([$build_vendor], [BuildVendor])
     GHC_CONVERT_OS([$build_os], [BuildOS])
 fi
-host=`echo "$host" | sed -e 's/linux-gnu/linux/' -e 's/-pc-/-unknown-/'`
+host=`echo "$host" | sed -e 's/linux-gnu/linux/' -e 's/-pc-/-unknown-/' -e 's/-gentoo-/-unknown-/' -e 's/freebsd.*$/freebsd/'`
 [host=`echo "$host" | sed -e 's/i[4-6]86/i386/'`] # escaping square bracket
 
 if test "$host_alias" = ""
@@ -282,7 +282,7 @@ else
     GHC_CONVERT_VENDOR([$host_vendor], [HostVendor])
     GHC_CONVERT_OS([$host_os], [HostOS])
 fi
-target=`echo "$target" | sed -e 's/linux-gnu/linux/' -e 's/-pc-/-unknown-/'`
+target=`echo "$target" | sed -e 's/linux-gnu/linux/' -e 's/-pc-/-unknown-/' -e 's/-gentoo-/-unknown-/' -e 's/freebsd.*$/freebsd/'`
 [target=`echo "$target" | sed -e 's/i[4-6]86/i386/'`] # escaping square bracket
 
 if test "$target_alias" = ""