crt: Use F_LD64 for long double functions. #20

Job	Run time
llvm-mingw (ucrt)	23m 23s
llvm-mingw (msvcrt)	23m 42s
llvm-mingw (ucrtbase)	23m 53s
gcc (ucrt, i686)	26m 17s
gcc (ucrt, x86_64)	27m 2s
gcc (msvcrt, i686)	26m 35s
gcc (msvcrt, x86_64)	28m 55s
test-libcxx (x86_64, i686-w64-mingw32-)	1h 9m 40s
test-libcxx (x86_64)	1h 10m 11s
test-llvm-mingw (x86_64, ucrtbase)	3m 27s
test-llvm-mingw (x86_64, msvcrt)	3m 42s
test-llvm-mingw (x86_64, ucrt)	3m 30s
test-llvm-mingw (i686, ucrt)	3m 32s
test-llvm-mingw (i686, ucrtbase)	3m 40s
test-ffmpeg (i686)	17m 6s
test-llvm-mingw (i686, msvcrt)	3m 29s
linux-test-cross-build-ffmpeg (i686)	5m 4s
test-ffmpeg (x86_64)	17m 27s
linux-test-cross-build-ffmpeg (aarch64)	4m 45s
linux-test-cross-build-ffmpeg (x86_64)	6m 1s
linux-test-cross-build-ffmpeg (armv7)	4m 21s
gcc-cross (msvcrt, i686)	23m 30s
gcc-cross (ucrt, x86_64)	19m 28s
gcc-cross (msvcrt, x86_64)	19m 18s
gcc-cross (ucrt, i686)	18m 46s
test-gcc (msvcrt, x86_64)	48s
test-gcc (ucrt, x86_64)	1m 1s
test-gcc (msvcrt, i686)	34s
test-gcc (ucrt, i686)	34s
	7h 59m 41s

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