A ‘Clean’ Workaround
TL;DR
1.
In Your assets/styles/main.scss insert at the top of the file (yes, before @import "common/variables";, we need the functions for str-replace()):
@import "~bootstrap/scss/functions";
@import "~bootstrap/scss/variables";
2.
In Your styles/common/_variables.scss insert:
$navbar-dark-toggler-icon-bg: url("data:image/svg+xml;charset=utf8,%3Csvg viewBox='0 0 30 30' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath stroke='#{str-replace(str-replace(#{$navbar-dark-color}, "(", "%28"), ")", "%29")}' stroke-width='2' stroke-linecap='round' stroke-miterlimit='10' d='M4 7h22M4 15h22M4 23h22'/%3E%3C/svg%3E");
$navbar-light-toggler-icon-bg: url("data:image/svg+xml;charset=utf8,%3Csvg viewBox='0 0 30 30' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath stroke='#{str-replace(str-replace(#{$navbar-light-color}, "(", "%28"), ")", "%29")}' stroke-width='2' stroke-linecap='round' stroke-miterlimit='10' d='M4 7h22M4 15h22M4 23h22'/%3E%3C/svg%3E");
Detail
The Problem aren’t the spaces. The brackets from the stroke='#{$navbar-dark-color}' causes the problem. So if we str-replace() the ( with %28 and the ) with %29 you can run yarn run build:production without removing your scss.