meson: correctly embed sandbox shell when asked

Change-Id: I2f6c0d42245204a516d2e424eea26a6391e975ad

meson.build

@@ -284,6 +284,16 @@ endif
 # Used to workaround https://github.com/mesonbuild/meson/issues/2320 in src/nix/meson.build.
 installcmd = find_program('install')
 
+enable_embedded_sandbox_shell = get_option('enable-embedded-sandbox-shell')
+if enable_embedded_sandbox_shell
+  # This one goes in config.h
+  # The path to busybox is passed as a -D flag when compiling libstore.
+  # Idk why, ask the old buildsystem.
+  configdata += {
+    'HAVE_EMBEDDED_SANDBOX_SHELL': 1,
+  }
+endif
+
 sandbox_shell = get_option('sandbox-shell')
 # Consider it required if we're on Linux and the user explicitly specified a non-default value.
 sandbox_shell_required = sandbox_shell != 'busybox' and host_machine.system() == 'linux'

meson.options

@@ -7,8 +7,8 @@ option('enable-build', type : 'boolean', value : true,
 option('gc', type : 'feature',
   description : 'enable garbage collection in the Nix expression evaluator (requires Boehm GC)',
 )
-# TODO(Qyriad): is this feature maintained?
-option('embedded-sandbox-shell', type : 'feature',
+
+option('enable-embedded-sandbox-shell', type : 'boolean', value : false,
   description : 'include the sandbox shell in the Nix binary',
 )
 

package.nix

@@ -182,6 +182,7 @@ stdenv.mkDerivation (finalAttrs: {
     lib.optionals (buildWithMeson && stdenv.hostPlatform.isLinux) [
       "-Dsandbox-shell=${lib.getBin busybox-sandbox-shell}/bin/busybox"
     ]
+    ++ lib.optional stdenv.hostPlatform.isStatic "-Denable-embedded-sandbox-shell=true"
     ++ lib.optional (finalAttrs.dontBuild) "-Denable-build=false"
     # mesonConfigurePhase automatically passes -Dauto_features=enabled,
     # so we must explicitly enable or disable features that we are not passing

src/libstore/meson.build

@@ -10,6 +10,24 @@ foreach header : [ 'schema.sql', 'ca-specific-schema.sql' ]
   )
 endforeach
 
+if enable_embedded_sandbox_shell
+  hexdump = find_program('hexdump', required : true)
+  embedded_sandbox_shell_gen = custom_target(
+    'embedded-sandbox-shell.gen.hh',
+    command : [
+      hexdump,
+      '-v',
+      '-e',
+      '1/1 "0x%x," "\n"'
+    ],
+    input : busybox.full_path(),
+    output : 'embedded-sandbox-shell.gen.hh',
+    capture : true,
+    feed : true,
+  )
+  libstore_generated_headers += embedded_sandbox_shell_gen
+endif
+
 libstore_sources = files(
   'binary-cache-store.cc',
   'build-result.cc',