[toolchain] Add +nofdiv flag to LLVM #1322

Job	Run time
riscv-isa-sim	14s
check-opcodes	5s
tc-gcc	2m 2s
tc-llvm	1h 25m 25s
verilator	11s
verilator-model (minpool)	4m 29s
verilator-model (mempool)	11m 9s
check-bootrom	22s
build-apps-gcc (minpool)	1m 7s
build-apps-omp (minpool)	37s
build-apps-gcc (mempool)	51s
build-apps-omp (mempool)	38s
unit-test	2m 24s
run-apps-gcc (minpool)	26s
run-apps-gcc (mempool)	2m 47s
tc-halide	13s
build-apps-llvm (minpool)	1m 34s
build-apps-llvm (mempool)	1m 43s
build-apps-halide (minpool)	1m 14s
build-apps-halide (mempool)	1m 7s
run-apps-halide (minpool)	39s
run-apps-halide (mempool)	2m 55s
run-apps-llvm (minpool)	35s
run-apps-llvm (mempool)	2m 53s
clean-up-compile-runs (minpool)	2s
clean-up-compile-runs (mempool)	3s
clean-up	3s
	2h 5m 48s

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