Problem building firefox 75 on 9-stable (i386 and amd64)

[Mike Pumford <mpumford%mudcovered.org.uk@localhost>]

Getting the following build error building firefox on 9-stable. No 
package options set for anything and its a totally clean chroot build 
environment.

/comp/obj/pkgsrc/www/firefox/work/build/dist/include/nss/mozpkix/pkixtypes.h:28:10: 
fatal error: 'memory' file not found
/comp/obj/pkgsrc/www/firefox/work/build/dist/include/nss/mozpkix/pkixtypes.h:28:10: 
fatal error: 'memory' file not found, err: true
thread 'main' panicked at 'unable to generate bindings: ()', 
/comp/obj/pkgsrc/www/firefox/work/firefox-75.0/third_party/rust/neqo-crypto/build.rs:273:20
stack backtrace:
   0:        0x156de2582 - 
<std::sys_common::backtrace::_print::DisplayBacktrace as 
core::fmt::Display>::fmt::hfc6622696269221b
   1:        0x156dfca3d - core::fmt::write::hd3eed79e7afa73cf
   2:        0x156de1815 - std::io::Write::write_fmt::h60ea7d9604ed82bb
   3:        0x156dd5590 - 
std::panicking::default_hook::{{closure}}::h2c07f5fe2b4f82c2
   4:        0x156dd5282 - std::panicking::default_hook::h6dd6fafda250b80f
   5:        0x156dd5cc0 - 
std::panicking::rust_panic_with_hook::hd4a4901bf3898ce4
   6:        0x156dd57d0 - rust_begin_unwind
   7:        0x156e01fc1 - core::panicking::panic_fmt::he26e900a02fe21cb
   8:        0x156e02053 - core::result::unwrap_failed::he7e5ca430592568d
   9:        0x156c49c29 - build_script_build::main::h52cc2ede9232a29c
  10:        0x156c34fc3 - 
std::rt::lang_start::{{closure}}::hc04ed389f77ffa29
  11:        0x156dd56b3 - std::panicking::try::do_call::hf264ae5e639af05c
  12:        0x156de8297 - __rust_maybe_catch_panic
  13:        0x156dd8cfb - std::rt::lang_start_internal::h63883908f6b782bf
  14:        0x156c4a9d2 - main
  15:        0x156c3499d - ___start

1 error generated.
gmake[3]: *** 
[/comp/obj/pkgsrc/www/firefox/work/firefox-75.0/config/makefiles/rust.mk:290: 
force-cargo-library-build] Error 101
gmake[3]: Leaving directory 
'/comp/obj/pkgsrc/www/firefox/work/build/toolkit/library/rust'
gmake[2]: *** 
[/comp/obj/pkgsrc/www/firefox/work/firefox-75.0/config/recurse.mk:74: 
toolkit/library/rust/target] Error 2
gmake[3]: *** 
[/comp/obj/pkgsrc/www/firefox/work/firefox-75.0/config/rules.mk:747: 
Unified_cpp_js_src_jit11.o] Error 1
1 error generated.
gmake[3]: *** 
[/comp/obj/pkgsrc/www/firefox/work/firefox-75.0/config/rules.mk:747: 
Unified_cpp_js_src_jit12.o] Error 1
1 error generated.
gmake[3]: *** 
[/comp/obj/pkgsrc/www/firefox/work/firefox-75.0/config/rules.mk:747: 
Unified_cpp_js_src_jit13.o] Error 1
gmake[3]: Leaving directory 
'/comp/obj/pkgsrc/www/firefox/work/build/js/src/jit'
gmake[2]: *** 
[/comp/obj/pkgsrc/www/firefox/work/firefox-75.0/config/recurse.mk:74: 
js/src/jit/target-objects] Error 2
gmake[2]: Leaving directory '/comp/obj/pkgsrc/www/firefox/work/build'
gmake[1]: *** 
[/comp/obj/pkgsrc/www/firefox/work/firefox-75.0/config/recurse.mk:34: 
compile] Error 2
gmake[1]: Leaving directory '/comp/obj/pkgsrc/www/firefox/work/build'
gmake: *** 
[/comp/obj/pkgsrc/www/firefox/work/firefox-75.0/config/rules.mk:394: 
all] Error 2
*** Error code 2

Stop.
make[1]: stopped in /usr/pkgsrc/www/firefox
*** Error code 1

Looking at the full log it looks like rust is trying to compile C++ 
files and utterly failing to find the C++ standard library headers

I've got full build logs for both firefox (and all of its dependencies 
if they are needed). I've also got a snapshot of the firefox package 
build environment so if anyone wants me to check on anything in that I can.

Mike