You said:
0:03.33 error: failed to select a version for getrandom.
0:03.33 ... required by package mozilla-central-workspace-hack v0.1.0 (/var/tmp/portage/www-client/firefox-115.31.0/work/firefox-115.31.0/build/workspace-hack)
0:03.33 ... which satisfies path dependency mozilla-central-workspace-hack (locked to 0.1.0) of package jsrust_shared v0.1.0 (/var/tmp/portage/www-client/firefox-115.31.0/work/firefox-115.31.0/js/src/rust/shared)
0:03.33 ... which satisfies path dependency jsrust_shared (locked to 0.1.0) of package jsrust v0.1.0 (/var/tmp/portage/www-client/firefox-115.31.0/work/firefox-115.31.0/js/src/rust)
0:03.33 versions that meet the requirements >=0.2 are: 0.3.3
0:03.33 the package mozilla-central-workspace-hack depends on getrandom, with features: custom but getrandom does not have these features.
0:03.33 failed to select a version for getrandom which could resolve this conflict