This patch incorporates feedback from IRC (many fixlets). I rebased it onto the core-updates branch. The webengine fails with an error I fail to understand: make[3]: Entering directory '/tmp/guix-build-qtwebengine-5.14.2.drv-0/qtwebengine-everywhere-src-5.14.2/src/core' ninja -k1 -j12 -C /tmp/guix-build-qtwebengine-5.14.2.drv-0/qtwebengine-everywhere-src-5.14.2/src/core/release QtWebEngineCore ninja: Entering directory `/tmp/guix-build-qtwebengine-5.14.2.drv-0/qtwebengine-everywhere-src-5.14.2/src/core/release' ninja: error: '../../3rdparty/chromium/third_party/boringssl/linux-x86_64/crypto/third_party/sike/asm/fp-x86_64.S', needed by 'host/obj/third_party/boringssl/boringssl_asm/fp-x86_64.o', missing and no known rule to make it