community/mlt: fix deadlock due to recursive mutex

See: alpine/aports#11838 (comment 114554)

cherry picked from commit 9558f935
7 jobs for !12640 with mlt-fix-mutex-3.12-stable in 3 minutes and 49 seconds (queued for 1 second)
detached
Status Job ID Name Coverage
  Lint
failed #210367
x86_64 docker-alpine allowed to fail
lint

00:00:20

 
  Build
passed #210372
aarch64 ci-build docker-alpine
build-aarch64

00:01:49

passed #210373
armv7 ci-build docker-alpine
build-armv7

00:02:37

passed #210371
ppc64le ci-build docker-alpine
build-ppc64le

00:03:28

passed #210370
s390x ci-build docker-alpine
build-s390x

00:01:22

passed #210369
x86 ci-build docker-alpine
build-x86

00:01:27

passed #210368
x86_64 ci-build docker-alpine
build-x86_64

00:01:14

 
Name Stage Failure
failed
lint Lint
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apkbuild-lint:
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MP:[AL56]:APKBUILD:Patch file ./musl-locale.patch is missing a description

Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1