configure: update list of preserved environment variables

INSTALL and LIBTOOL are not used anymore, but OBJCFLAGS is new and
was not listed.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/configure b/configure
index 4b12a80..d41c7ed 100755 (executable)
--- a/configure
+++ b/configure
@@ -2722,13 +2722,12 @@ preserve_env CC
 preserve_env CFLAGS
 preserve_env CXX
 preserve_env CXXFLAGS
-preserve_env INSTALL
 preserve_env LD
 preserve_env LDFLAGS
 preserve_env LD_LIBRARY_PATH
-preserve_env LIBTOOL
 preserve_env MAKE
 preserve_env NM
+preserve_env OBJCFLAGS
 preserve_env OBJCOPY
 preserve_env PATH
 preserve_env PKG_CONFIG