Remove the only actual obsolete bit of that patch

Former-commit-id: 3478365b2e1679d28ebf1b0bbbcc9fae3354279b

debian/patches/conditionally_define_alignas_for_precise.patch

@@ -48,17 +48,3 @@ index 4e63c89..8875b10 100644
    else()
      set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -stdlib=libc++ ${C_CXX_FLAGS}")
    endif()
-diff --git a/external/boringssl/CMakeLists.txt b/external/boringssl/CMakeLists.txt
-index 4e63c89..296d010 100644
---- a/external/boringssl/CMakeLists.txt
-+++ b/external/boringssl/CMakeLists.txt
-@@ -198,7 +198,9 @@ add_subdirectory(ssl)
- if(ENABLE_TESTS)
- add_subdirectory(ssl/test)
- endif()
-+if(ENABLE_TOOL)
- add_subdirectory(tool)
-+endif()
- if(ENABLE_DECREPIT)
- add_subdirectory(decrepit)
- endif()