dav1dplay: Add -lm for llround() support

Neither --buildtype=plain nor --buildtype=debug set -ffast-math, so
llround() is kept as a function call and isn’t optimised out into
cvttsd2siq (on amd64), thus requiring the math lib to be linked.

Note that even with -ffast-math, it isn’t guaranteed that a call to
llround() will always be omitted (I have reproduced this on PowerPC), so
this fix is correct even if we ever decide to enable -ffast-math in
other build types.
34 jobs for master in 4 minutes and 37 seconds (queued for 6 seconds)
Status Job ID Name Coverage
  Style
passed style-check #548396
amd64 docker

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passed x86inc-check #548397
amd64 docker

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  Build
passed build-android-aarch64 #548409
amd64 docker

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passed build-android-armv7 #548408
amd64 docker

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passed build-debian #548398
amd64 avx2 docker

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passed build-debian-aarch64 #548410
aarch64 docker

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passed build-debian-aarch64-clang-5 #548411
aarch64 docker

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passed build-debian-armv7 #548414
armv7 docker

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passed build-debian-armv7-clang-5 #548415
armv7 docker

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passed build-debian-examples #548401
amd64 docker

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passed build-debian-no-tools #548402
amd64 docker

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passed build-debian-ppc64le #548417
ppc64le docker

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passed build-debian-static #548399
amd64 docker

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passed build-debian-werror #548413
aarch64 docker

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passed build-debian32 #548400
amd64 docker

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passed build-macos #548412
catalina amd64

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passed build-ubuntu-snap #548416
amd64 docker

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passed build-win-arm32 #548406
amd64 docker

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passed build-win-arm64 #548407
amd64 docker

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passed build-win32 #548403
amd64 docker

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passed build-win32-unaligned-stack #548404
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passed build-win64 #548405
amd64 docker

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  Test
passed test-debian #548418
amd64 docker

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95.8046%
passed test-debian-aarch64 #548427
aarch64 docker

00:00:27

passed test-debian-armv7-clang-5 #548429
armv7 docker

00:01:09

passed test-debian-asan #548422
amd64 docker

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passed test-debian-asm #548419
avx2 amd64 docker

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passed test-debian-msan #548423
amd64 docker

00:01:24

passed test-debian-ppc64le #548428
ppc64le docker

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passed test-debian-tsan #548425
amd64 docker

00:02:55

passed test-debian-ubsan #548424
amd64 docker

00:01:44

passed test-debian-unaligned-stack #548421
amd64 avx2 docker

00:00:39

passed test-debian32-asm #548420
avx2 amd64 docker

00:01:09

passed test-win64 #548426
amd64 avx2 docker

00:01:30