Add a Meson build system

This allows bwrap to be built as a subproject in larger Meson projects.
When built as a subproject, we install into the --libexecdir and
require a program prefix to be specified: for example, Flatpak would use
program_prefix=flatpak- to get /usr/libexec/flatpak-bwrap. Verified to
be backwards-compatible as far as Meson 0.49.0 (Debian 9 backports).

Loosely based on previous work by Jussi Pakkanen (see #133).

Differences between the Autotools and Meson builds:

The Meson build requires a version of libcap that has pkg-config
metadata (introduced in libcap 2.23, in 2013).

The Meson build has no equivalent of --with-priv-mode=setuid. On
distributions like Debian <= 10 and RHEL <= 7 that require a setuid bwrap
executable, the sysadmin or distribution packaging will need to set the
correct permissions on the bwrap executable; Debian already did this via
packaging rather than the upstream build system.

The Meson build supports being used as a subproject, and there is CI
for this. It automatically disables shell completions and man pages,
moves the bubblewrap executable to ${libexecdir}, and renames the
bubblewrap executable according to a program_prefix option that the
caller must specify (for example, Flatpak would use
-Dprogram_prefix=flatpak- to get /usr/libexec/flatpak-bwrap). See the
tests/use-as-subproject/ directory for an example.

Signed-off-by: Simon McVittie <smcv@collabora.com>

5 files changed, 26 insertions, 0 deletions

diff --git a/tests/use-as-subproject/.gitignore b/tests/use-as-subproject/.gitignore
new file mode 100644
index 0000000..371a7d9
--- /dev/null
+++ b/tests/use-as-subproject/.gitignore
@@ -0,0 +1,2 @@
+/_build/
+/subprojects/
diff --git a/tests/use-as-subproject/README b/tests/use-as-subproject/README
new file mode 100644
index 0000000..97d2e88
--- /dev/null
+++ b/tests/use-as-subproject/README
@@ -0,0 +1,3 @@
+This is a simple example of a project that uses bubblewrap as a
+subproject. The intention is that if this project can successfully build
+bubblewrap as a subproject, then so could Flatpak.
diff --git a/tests/use-as-subproject/config.h b/tests/use-as-subproject/config.h
new file mode 100644
index 0000000..4a99af4
--- /dev/null
+++ b/tests/use-as-subproject/config.h
@@ -0,0 +1 @@
+#error Should not use superproject config.h to compile bubblewrap
diff --git a/tests/use-as-subproject/dummy-config.h.in b/tests/use-as-subproject/dummy-config.h.in
new file mode 100644
index 0000000..1d1e56a
--- /dev/null
+++ b/tests/use-as-subproject/dummy-config.h.in
@@ -0,0 +1 @@
+#error Should not use superproject generated config.h to compile bubblewrap
diff --git a/tests/use-as-subproject/meson.build b/tests/use-as-subproject/meson.build
new file mode 100644
index 0000000..802fd61
--- /dev/null
+++ b/tests/use-as-subproject/meson.build
@@ -0,0 +1,19 @@
+project(
+  'use-bubblewrap-as-subproject',
+  'c',
+  version : '0',
+  meson_version : '>=0.49.0',
+)
+
+configure_file(
+  output : 'config.h',
+  input : 'dummy-config.h.in',
+  configuration : configuration_data(),
+)
+
+subproject(
+  'bubblewrap',
+  default_options : [
+    'program_prefix=not-flatpak-',
+  ],
+)