Make improvements

- Introduce portable sched_getcpu() api
- Support GCC's __target_clones__ feature
- Make fma() go faster on x86 in default mode
- Remove some asan checks from core libraries
- WinMain() now ensures $HOME and $USER are defined

build/bootstrap/gcc-only-flags.txt

@@ -0,0 +1,58 @@
+--nocompress-debug-sections
+--noexecstack
+-Wa,--nocompress-debug-sections
+-Wa,--noexecstack
+-Wa,-msse2avx
+-Werror=maybe-uninitialized
+-Wno-literal-suffix
+-Wno-unused-but-set-variable
+-Wunsafe-loop-optimizations
+-fbranch-target-load-optimize
+-fcx-limited-range
+-fdelete-dead-exceptions
+-femit-struct-debug-baseonly
+-ffp-int-builtin-inexact
+-finline-functions-called-once
+-fipa-pta
+-fivopts
+-flimit-function-alignment
+-fmerge-constants
+-fmodulo-sched
+-fmodulo-sched-allow-regmoves
+-fno-align-jumps
+-fno-align-labels
+-fno-align-loops
+-fno-code-hoisting
+-fno-cx-limited-range
+-fno-fp-int-builtin-inexact
+-fno-gnu-unique
+-fno-inline-functions-called-once
+-fno-instrument-functions
+-fno-schedule-insns2
+-fno-whole-program
+-fopt-info-vec
+-fopt-info-vec-missed
+-freg-struct-return
+-freschedule-modulo-scheduled-loops
+-frounding-math
+-fsched2-use-superblocks
+-fschedule-insns
+-fschedule-insns2
+-fshrink-wrap
+-fshrink-wrap-separate
+-fsignaling-nans
+-fstack-clash-protection
+-ftracer
+-ftrapv
+-ftree-loop-im
+-ftree-loop-vectorize
+-funsafe-loop-optimizations
+-fversion-loops-for-strides
+-fwhole-program
+-gdescribe-dies
+-gstabs
+-mcall-ms2sysv-xlogues
+-mdispatch-scheduler
+-mfpmath=sse+387
+-mmitigate-rop
+-mno-fentry