AM_PROG_VALAC shouldn't be used in distributed packages

[JM]

Hello
I refer to this macro:
http://www.gnu.org/software/hello/manual/automake/Vala-Support.html

The AM_PROG_VALAC macro checks for the required version of the vala
compiler. 
"... Any .vala file listed in a _SOURCES variable will be compiled into
C code by the Vala compiler. The generated .c files are distributed. The
end user does not need to have a Vala compiler installed."

I have a problem with the distributed tarballs of my program. Consider
the following example:
I use this in my configure.ac:

VALA_REQUIRED=0.9.8
AM_PROG_VALAC($VALA_REQUIRED)

I do my program for vala-0.9.8 and I do a 'make dist' -> c files are
distributed with the tarball.

On the targeted users machine there is vala-0.9.7, the user does
'./configure' and is getting:
 $ ./configure
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for a thread-safe mkdir -p... /bin/mkdir -p
checking for gawk... gawk
checking whether make sets $(MAKE)... yes
checking whether to enable maintainer-specific portions of Makefiles...
no
checking for valac... /usr/local/bin/valac
checking /usr/local/bin/valac is at least version 0.9.8... no
configure: error: Vala 0.9.8 not found.

But the user should be able to build the program. vala is not necessary
to have on his machine at all.

I tried to check for the vala pkg-config data but this failed on a
ubuntu distribution where there is the vala compiler but not the *-dev
package with the *.pc file. So I cannot workaround here.



In the distributed package, the installed version of vala shouldn't
matter, because the vala compiler is not needed at all (it also
shouldn't be used at all). It's not easy to understand that if you have
an old version of vala, the build of the package will fail and if you
uninstall the old vala version it will work.

I'm not an autotools expert but I am willing to help fix this but I will
need further instructions.
automake is version 1.11.1
Regards
Jörn