It’s taken years to get Chrome to start compiling, not least because of the dependency tree that needed sorting. A more trying problem was that Chrome uses SCONS via gyp to set up the development environment. Cruelly, scons uses its own $PATH variable which it determines of its own accord. This meant that all of the dependencies that I’d built into /local/usr weren’t being referenced in the SCONS path. Additionally, editing the scons files themselves with the PATH setting didn’t work because they were regenerated by gyp at each reinitialising of the environment. Eventually after much trial and error I found a workaround in editing the src/build/common.gypi file to include the line:
'ENV': {'PATH': '/custom/path/variable/here'},
Within the scons_variable_settings block for linux.