elf: ignore EH_FRAME segments

PT_GNU_EH_FRAME segments are contained within PT_LOAD segments, and
so need not be loaded.  Moreover, when we load a segment, we align
it to page boundaries; this overwrites previous contents.  Does
serious damage with small objects (like tst-dir.so) - overwriting
the main function.

Fix by ignoring EH_FRAME segments (libunwind will later re-discover
them when iterating over the objects's phdrs).

elf.cc

@@ -206,15 +206,13 @@ namespace elf {
             case PT_PHDR:
             case PT_GNU_STACK:
             case PT_GNU_RELRO:
+            case PT_GNU_EH_FRAME:
                 break;
             case PT_TLS:
                 _tls_segment = _base + phdr.p_vaddr;
                 _tls_init_size = phdr.p_filesz;
                 _tls_uninit_size = phdr.p_memsz - phdr.p_filesz;
                 break;
-            case PT_GNU_EH_FRAME:
-                load_segment(phdr);
-                break;
             default:
                 abort();
                 throw std::runtime_error("bad p_type");