build-unit-test-docker: boost: switch mirror to yocto

The official download location for boost, bintray, often runs out
of bandwidth and gives errors when we download from it.  Switch
our download location to be the yoctoproject mirror instead, which
seems to be more stable.

The downside of this is that we can only use Boost releases which
are already incorporated into a Yocto commit, but we really should
only do that anyhow.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ia028ed18d7ef4b9d2a0cc3ca351cee27073ad6bc
diff --git a/scripts/build-unit-test-docker b/scripts/build-unit-test-docker
index ebede4a..467b02d 100755
--- a/scripts/build-unit-test-docker
+++ b/scripts/build-unit-test-docker
@@ -80,7 +80,7 @@
     "boost": PackageDef(
         rev="1.75.0",
         url=(
-            lambda pkg, rev: f"https://dl.bintray.com/boostorg/release/{rev}/source/{pkg}_{rev.replace('.', '_')}.tar.bz2"
+            lambda pkg, rev: f"https://downloads.yoctoproject.org/mirror/sources/{pkg}_{rev.replace('.', '_')}.tar.bz2"
         ),
         build_type="custom",
         build_steps=[