all: update to LLVM 14

Switch over to LLVM 14 for static builds. Keep using LLVM 13 for regular
builds for now.

This uses a branch of the upstream Espressif branch to fix an issue,
see: https://github.com/espressif/llvm-project/pull/59

targets/esp8266.json

@@ -1,6 +1,7 @@
 {
 	"inherits": ["xtensa"],
 	"cpu": "esp8266",
+	"features": "+debug,+density,+exception,+extendedl32r,+highpriinterrupts,+interrupt,+mul32,+nsa,+prid,+regprotect,+rvector,+timerint",
 	"build-tags": ["esp8266", "esp"],
 	"scheduler": "tasks",
 	"linker": "xtensa-esp32-elf-ld",