Undefined simbols moz_xmalloc (et al.) in Gecko 12

Hi everybody,

I am updating our embedding app from Gecko7 to Gecko12. I get linking
errors:

In function `operator new(unsigned int)':
/dist/include/mozilla/mozalloc.h:229: undefined reference to
`moz_xmalloc'

In function `operator new[](unsigned int)':
/dist/include/mozilla/mozalloc.h:241: undefined reference to
`moz_xmalloc'

In function `operator delete(void*)':
/dist/include/mozilla/mozalloc.h:253: undefined reference to
`moz_free'

In function `operator delete[](void*)':
dist/include/mozilla/mozalloc.h:265: undefined reference to `moz_free'

I am building xulrunner with a default .mozconfig, with just

ac_add_options --enable-cpp-rtti

added.

Any advice (apart from copying the sources and forcing the compilation/
linking, which I will do now) ?

Thanks,
Aaron