build: Cleanups and fixes for a newer clang toolchain (osquery#8412)

- Force the use of the DWARF debug symbols version 4,
  since only very recent versions of gdb support any version higher than
  that and on newer clang versions, 5 is the default.

- Correct the secure_getenv check; GLIBC 2.17 is the first version
  that adds supports for it, so it should be included

- Move the selection of the standard library implementation and
  corollary library on Linux to be a toolchain specific setting,
  making it slightly easier to build with a different toolchain.

cmake/flags.cmake

@@ -84,11 +84,9 @@ function(setupBuildFlags)
       -Woverloaded-virtual
       -Wnon-virtual-dtor
       -Weffc++
-      -stdlib=libc++
     )
 
     set(posix_cxx_link_options
-      -stdlib=libc++
       -ldl
     )
 
@@ -179,7 +177,6 @@ function(setupBuildFlags)
       )
 
       set(linux_cxx_link_libraries
-        c++abi.a
         rt
         dl
       )

cmake/toolchain.cmake

@@ -8,6 +8,9 @@ if(OSQUERY_TOOLCHAIN_SYSROOT)
   overwrite_cache_variable("CMAKE_CXX_LINK_PIE_SUPPORTED" "INTERNAL" "TRUE")
   overwrite_cache_variable("CMAKE_C_LINK_NO_PIE_SUPPORTED" "INTERNAL" "TRUE")
   overwrite_cache_variable("CMAKE_C_LINK_PIE_SUPPORTED" "INTERNAL" "TRUE")
+  overwrite_cache_variable("CMAKE_CXX_FLAGS_INIT" "STRING" "-stdlib=libc++ -gdwarf-4")
+  overwrite_cache_variable("CMAKE_C_FLAGS_INIT" "STRING" "-gdwarf-4")
+  overwrite_cache_variable("CMAKE_EXE_LINKER_FLAGS" "STRING" "-stdlib=libc++ -lc++abi")
 else()
   option(OSQUERY_STATIC_BUILD "Whether to prefer linking static libraries or not")
 

osquery/tables/system/linux/rpm_packages.cpp

@@ -26,7 +26,7 @@
 #include <osquery/worker/logging/glog/glog_logger.h>
 
 // librpm may be configured and compiled with glibc < 2.17.
-#if defined(__GLIBC__) && __GLIBC_MINOR__ > 17
+#if defined(__GLIBC__) && __GLIBC_MINOR__ >= 17
 extern "C" char* __secure_getenv(const char* _s) __attribute__((weak));
 extern "C" char* __secure_getenv(const char* _s) {
   return secure_getenv(_s);