Use system liblzma but bundled libunwind on Ubuntu

D66446570 disabled using the system liblzma, libunwind and glog
packages on Ubuntu due to them causing watchman's tests to hang
when run in GitHub Actions, and D86604386 confirmed this still
happens with Ubuntu Noble.

The original investigation noted that Fedora 40 didn't exhibit
this behavior. The main difference I see is that Fedora 40 packages
libunwind 1.8.0 while Ubuntu Jammy packages 1.3.2 and Noble 1.6.2.
Fedora also doesn't build its libunwind with liblzma support.
However, the autotools build system in libunwind tries to enable
minidebuginfo support by default, which is what looks for liblzma,
so the CI has been using libunwind built with liblzma support anyways.
Thus I think the cause is not the liblzma package in Ubuntu but rather
the old libunwind version.

Building these deps from source via getdeps has been rather painful for OSS consumers
since it produces shared object libraries that needs to be shipped alongside
watchman. See #1276, #1273
for resulting complaints. Conveniently, as of last week we should automatically build
and consume a static libunwind thanks to D93644457, so that issue should solve itself
once GitHub Actions caches expire. So, let's allow using system liblzma on Ubuntu
and update the other comments to incriminate libunwind instead of liblzma.

Tested at https://github.com/mszabo-wikia/watchman/actions/runs/22643456785/job/65625279878?pr=1

Fixes #1276, fixes #1273.

Author: mszabo-wikia

build/fbcode_builder/manifests/glog

@@ -24,7 +24,7 @@ HAVE_TR1_UNORDERED_SET=OFF
 [homebrew]
 glog
 
-# on ubuntu glog brings in liblzma-dev, which in turn breaks watchman tests
+# on ubuntu this pulls in libunwind < 1.8.0 which breaks watchman tests
 [debs.not(distro=ubuntu)]
 libgoogle-glog-dev
 

build/fbcode_builder/manifests/libunwind

@@ -5,7 +5,7 @@ name = libunwind
 libunwind-devel
 libunwind
 
-# on ubuntu this brings in liblzma-dev, which in turn breaks watchman tests
+# libunwind < 1.8.0 breaks watchman tests
 [debs.not(distro=ubuntu)]
 libunwind-dev
 

build/fbcode_builder/manifests/xz

@@ -1,8 +1,7 @@
 [manifest]
 name = xz
 
-# ubuntu's package causes watchman's tests to hang
-[debs.not(distro=ubuntu)]
+[debs]
 liblzma-dev
 
 [homebrew]