lc-compliance: Build with gtest in subprojects

libgtest-dev is provided as a static library at least by Debian 10.
The compiler and linker to create the static library might be
different from ones used for libcamera. This causes a problem
upon linking.

This puts gtest code to subprojects, builds the code and link it
for lc-compliance. However, libgtest is locally built as a library on
ChromeOS and thus the used compiler and linker are the same as one
used for libcamera. We don't do these on ChromeOS build environment.

Signed-off-by: Hirokazu Honda <hiroh@chromium.org>
Tested-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/lc-compliance/meson.build

@@ -1,13 +1,25 @@
 # SPDX-License-Identifier: CC0-1.0
 
 libevent = dependency('libevent_pthreads', required : get_option('lc-compliance'))
-libgtest = dependency('gtest', required : get_option('lc-compliance'))
 
-if not (libevent.found() and libgtest.found())
+if not libevent.found()
     lc_compliance_enabled = false
     subdir_done()
 endif
 
+if get_option('android_platform') == 'cros'
+    libgtest = dependency('gtest', required : get_option('lc-compliance'))
+
+    if not libgtest.found()
+        lc_compliance_enabled = false
+        subdir_done()
+    endif
+
+else
+    libgtest_sp = subproject('gtest')
+    libgtest = libgtest_sp.get_variable('gtest_dep')
+endif
+
 lc_compliance_enabled = true
 
 lc_compliance_sources = files([