build-doc: make work when run from subdirectories

This in particular had broken
./build --download-dependencies -aA -aa -ax all
not sure why, but there must be a change in directory somewhere then.

The only chdir we do in this repo was for ctng crap, I'm also restoring
that chdir back after we are done.

build

@@ -525,9 +525,21 @@ Which components to build. Default: qemu-buildroot
                     self.sh.add_newlines(sorted(python3_pkgs))
                 )
             if ruby_pkgs:
-                # TODO fails without sudo and with --local on Ubuntu 18.04.
+                # The right thing to do would be to use RVM and avoid sudo,
+                # but we felt it was too much boilerplate for now.
+                #
+                # --user-install does work here, but we still need to add
+                # the binary to PATH which is a pain:
+                # https://stackoverflow.com/questions/31596273/install-gem-in-local-folder
                 self.sh.run_cmd(['sudo', 'gem', 'install', 'bundler', LF])
-                self.sh.run_cmd(['bundle', 'install', LF])
+                # No ones knows how to do this without sudo:
+                # https://stackoverflow.com/questions/16376995/bundler-cannot-install-any-gems-without-sudo/27677094
+                self.sh.run_cmd([
+                    'sudo', LF,
+                    'bundle', LF,
+                    'install', LF,
+                    '--gemfile', os.path.join(self.env['root_dir'], 'Gemfile'), LF,
+                ])
             git_cmd_common = [
                 'git', LF,
                 'submodule', LF,

build-crosstool-ng

@@ -32,9 +32,9 @@ Build crosstool-NG with Newlib for bare metal compilation
             self.env['crosstool_ng_source_dir'],
             self.env['crosstool_ng_source_copy_dir'],
         )
-        os.chdir(self.env['crosstool_ng_source_copy_dir'])
         self.sh.run_cmd(
             [os.path.join(self.env['crosstool_ng_source_copy_dir'], 'bootstrap'), LF],
+            cwd=self.env['crosstool_ng_source_copy_dir'],
         )
         self.sh.run_cmd(
             [
@@ -44,8 +44,12 @@ Build crosstool-NG with Newlib for bare metal compilation
                 os.path.join(os.curdir, 'configure'), LF,
                 '--enable-local', LF,
             ],
+            cwd=self.env['crosstool_ng_source_copy_dir'],
+        )
+        self.sh.run_cmd(
+            ['make', '-j', str(self.env['nproc']), LF],
+            cwd=self.env['crosstool_ng_source_copy_dir'],
         )
-        self.sh.run_cmd(['make', '-j', str(self.env['nproc']), LF])
 
         # Build the toolchain.
         self.sh.cp(
@@ -65,6 +69,7 @@ Build crosstool-NG with Newlib for bare metal compilation
                 self.env['crosstool_ng_executable'], LF,
                 'defconfig', LF,
             ],
+            cwd=self.env['crosstool_ng_source_copy_dir'],
         )
         self.sh.rmrf(defconfig_dest)
         self.sh.run_cmd(
@@ -73,6 +78,7 @@ Build crosstool-NG with Newlib for bare metal compilation
                 'build', LF,
                 'CT_JOBS={}'.format(str(self.env['nproc'])), LF,
             ],
+            cwd=self.env['crosstool_ng_source_copy_dir'],
             out_file=os.path.join(build_dir, self.env['repo_short_id'] + '.log'),
             delete_env=['LD_LIBRARY_PATH'],
             extra_paths=[self.env['ccache_dir']],

build-doc

@@ -40,8 +40,8 @@ https://github.com/cirosantilli/linux-kernel-module-cheat#build-the-documentatio
             self.env['readme']
         ]).splitlines():
             if not external_link_re.match(link):
-                if not os.path.lexists(link):
-                    self.log_error('broken link: ' + link)
+                if not os.path.lexists(os.path.join(self.env['root_dir'], link)):
+                    self.log_error('broken link to local file: ' + link)
                     exit_status = 1
 
         # Check that non-README links to README IDs exit.
@@ -53,13 +53,16 @@ https://github.com/cirosantilli/linux-kernel-module-cheat#build-the-documentatio
             self.env['readme']
         ]).splitlines():
             header_ids.add(header_id)
-        for grep_line in self.sh.check_output([
-            'git',
-            'grep',
-            '--fixed-strings',
-            self.env['github_repo_id_url'] + '#',
-            LF
-        ]).splitlines():
+        for grep_line in self.sh.check_output(
+            [
+                'git',
+                'grep',
+                '--fixed-strings',
+                self.env['github_repo_id_url'] + '#',
+                LF
+            ],
+            cwd=self.env['root_dir']
+        ).splitlines():
             url_index = grep_line.index(self.env['github_repo_id_url'])
             hash_start_index = url_index + len(self.env['github_repo_id_url'])
             if len(grep_line) > hash_start_index: