cmds: remove unused lambda capture this

Remove a unused lambda capture on [this] in
anbox::cmds::CheckFeatures::CheckFeatures() and promote
-Wunused-lambda-capture back to error level on clang.

CMakeLists.txt

@@ -26,7 +26,6 @@ set(EXTRA_CXX_WARNINGS "-Wnon-virtual-dtor -Wold-style-cast")
 
 if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
   set(EXTRA_CXX_WARNINGS "${EXTRA_CXX_WARNINGS} -Wno-error=unused-const-variable")
-  set(EXTRA_CXX_WARNINGS "${EXTRA_CXX_WARNINGS} -Wno-error=unused-lambda-capture")
 endif()
 
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${C_AND_CXX_WARNINGS}")

src/anbox/cmds/check_features.cpp

@@ -42,7 +42,7 @@ anbox::cmds::CheckFeatures::CheckFeatures()
           cli::Name{"check-features"}, cli::Usage{"check-features"},
           cli::Description{"Check that the host system supports all necessary features"}} {
 
-  action([this](const cli::Command::Context&) {
+  action([](const cli::Command::Context&) {
 #if defined(CPU_FEATURES_ARCH_X86)
     const auto info = cpu_features::GetX86Info();
     std::vector<std::string> missing_features;