libxul and thunderbird build failing on 11.0-CURRENT, but firefox is ok

[Don Lewis]

I'm trying to use poudriere to build libxul and thunderbird on
11.0-CURRENT r286998 amd64.  The system has the latest jemalloc and
__FreeBSD_version is 1100079.  The ports tree is r395181, which has all
but the most recent Dragonfly tweak to Mk/bsd.gecko.mk.

I'm seeing the following error in the thunderbird build:

In file included from /wrkdirs/usr/ports/mail/thunderbird/work/comm-esr38/obj-x8
6_64-portbld-freebsd11.0/memory/mozalloc/Unified_cpp_memory_mozalloc0.cpp:2:
/wrkdirs/usr/ports/mail/thunderbird/work/comm-esr38/mozilla/memory/mozalloc/moza
lloc.cpp:212:12: error: use of undeclared identifier 'malloc_usable_size'; did y
ou mean 'moz_malloc_usable_size'?
    return malloc_usable_size(ptr);
           ^~~~~~~~~~~~~~~~~~
           moz_malloc_usable_size
/wrkdirs/usr/ports/mail/thunderbird/work/comm-esr38/mozilla/memory/mozalloc/moza
lloc.cpp:204:1: note: 'moz_malloc_usable_size' declared here
moz_malloc_usable_size(void *ptr)
^


The libxul build failure is very similar:

In file included from /wrkdirs/usr/ports/www/libxul/work/mozilla-esr38/obj-x86_6
4-portbld-freebsd11.0/memory/mozalloc/Unified_cpp_memory_mozalloc0.cpp:2:
/wrkdirs/usr/ports/www/libxul/work/mozilla-esr38/memory/mozalloc/mozalloc.cpp:21
2:12: error: use of undeclared identifier 'malloc_usable_size'; did you mean 'mo
z_malloc_usable_size'?
    return malloc_usable_size(ptr);
           ^~~~~~~~~~~~~~~~~~
           moz_malloc_usable_size
/wrkdirs/usr/ports/www/libxul/work/mozilla-esr38/memory/mozalloc/mozalloc.cpp:20
4:1: note: 'moz_malloc_usable_size' declared here
moz_malloc_usable_size(void *ptr)
^


The firefox build succeeds.