[readline, djgpp] Check $build_os instead of $host_os in configure

[Yao Qi <yao@codesourcery.com>]

Hi,
When I configure gdb as '--host=i586-pc-msdosdjgpp --target=i586-pc-msdosdjgpp'
on x86-linux, I get following configure error in readline.

   readline/configure: line 6268: pwd.exe: command not found

Looks like the configure script should check $build_os instead of
$host_os.  This patch is to fix this problem.  Is it OK?

Note that I am not sure that AC_CANONICAL_BUILD is necessary here, because
after I add it in configure.in, the re-generated configure is nearly
unchanged.

readline:

	* readline/configure.in: Invoke AC_CANONICAL_BUILD.
	Change $host_os to $build_os.
	* readline/configure: Regenerated.
---
 readline/configure    |    3 ++-
 readline/configure.in |    3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/readline/configure b/readline/configure
index 0187311..09de45d 100755
--- a/readline/configure
+++ b/readline/configure
@@ -2285,6 +2285,7 @@ case $host_os in *\ *) host_os=`echo "$host_os" | sed 's/ /-/g'`;; esac
 
 
 
+
 opt_curses=no
 opt_purify=no
 
@@ -6264,7 +6265,7 @@ fi
 
 
 
-case "$host_os" in
+case "$build_os" in
 msdosdjgpp*)	BUILD_DIR=`pwd.exe` ;;	# to prevent //d/path/file
 *)		BUILD_DIR=`pwd` ;;
 esac
diff --git a/readline/configure.in b/readline/configure.in
index f09f4e5..b395af4 100644
--- a/readline/configure.in
+++ b/readline/configure.in
@@ -39,6 +39,7 @@ dnl update the value of RL_READLINE_VERSION in readline.h when this changes
 LIBVERSION=6.2
 
 AC_CANONICAL_HOST
+AC_CANONICAL_BUILD
 
 dnl configure defaults
 opt_curses=no
@@ -268,7 +269,7 @@ AC_SUBST(SHARED_TARGET)
 AC_SUBST(STATIC_INSTALL_TARGET)
 AC_SUBST(SHARED_INSTALL_TARGET)
 
-case "$host_os" in
+case "$build_os" in
 msdosdjgpp*)	BUILD_DIR=`pwd.exe` ;;	# to prevent //d/path/file
 *)		BUILD_DIR=`pwd` ;;
 esac
-- 
1.7.7.6