Insync can’t open UI or blank UI (fix) (systems with glibc 2.34)

glibc 2.34 tries to use the clone3() syscall to create threads, creating an incompatibility with chromium/qtwebengine when it tries to run under a sandboxed environment. Until qtwebengine is updated to fallback to clone(), use this:

QTWEBENGINE_CHROMIUM_FLAGS="–no-sandbox" insync start