Generalize include path for dwarf.h (#790)

Summary:
Do not assume `dwarf.h` is contained within a subdirectory called `libdwarf` during CMake configure.

See https://github.com/facebook/folly/issues/788 for more detailed info.
Fixes: #788.
Pull Request resolved: https://github.com/facebook/folly/pull/790

Reviewed By: andrewjcg

Differential Revision: D9094892

Pulled By: yfeldblum

fbshipit-source-id: 6b5faf000e5ff4f85b2b93e43d12a911eb05b5ab

CMake/FindLibDwarf.cmake

-find_path(LIBDWARF_INCLUDE_DIR NAMES libdwarf/dwarf.h)
+find_path(LIBDWARF_INCLUDE_DIR NAMES dwarf.h)
 mark_as_advanced(LIBDWARF_INCLUDE_DIR)
 
 find_library(LIBDWARF_LIBRARY NAMES dwarf)

CMake/folly-deps.cmake

@@ -128,7 +128,7 @@ endif()
 find_package(LibDwarf)
 list(APPEND FOLLY_LINK_LIBRARIES ${LIBDWARF_LIBRARIES})
 list(APPEND FOLLY_INCLUDE_DIRECTORIES ${LIBDWARF_INCLUDE_DIRS})
-CHECK_INCLUDE_FILE_CXX(libdwarf/dwarf.h FOLLY_HAVE_LIBDWARF_DWARF_H)
+CHECK_INCLUDE_FILE_CXX(dwarf.h FOLLY_HAVE_LIBDWARF_DWARF_H)
 
 find_package(Libiberty)
 list(APPEND FOLLY_LINK_LIBRARIES ${LIBIBERTY_LIBRARIES})

folly/experimental/symbolizer/Dwarf.cpp

@@ -18,11 +18,7 @@
 
 #include <type_traits>
 
-#if FOLLY_HAVE_LIBDWARF_DWARF_H
-#include <libdwarf/dwarf.h>
-#else
-#include <dwarf.h> // @manual
-#endif
+#include <dwarf.h>
 
 namespace folly {
 namespace symbolizer {