LibELF: Allow (but ignore) PT_LOAD headers with zero size

GNU ld sometimes generates zero-sized PT_LOAD headers when running with
the "-z separate-code" option. Let's not choke on such headers, we can
just ignore them and move along.

Userland/Libraries/LibELF/DynamicLoader.cpp

@@ -260,6 +260,8 @@ void DynamicLoader::load_program_headers()
             VERIFY(!tls_region.has_value());
             tls_region = region;
         } else if (region.is_load()) {
+            if (region.size_in_memory() == 0)
+                return;
             load_regions.append(region);
             if (region.is_executable()) {
                 text_regions.append(region);

Userland/Libraries/LibELF/Validation.cpp

@@ -230,12 +230,6 @@ bool validate_program_headers(const ElfW(Ehdr) & elf_header, size_t file_size, c
             return false;
         }
 
-        if (program_header.p_memsz <= 0 && (program_header.p_type == PT_TLS || program_header.p_type == PT_LOAD)) {
-            if (verbose)
-                dbgln("Program header ({}) has invalid size in memory ({})", header_index, program_header.p_memsz);
-            return false;
-        }
-
         if (elf_header.e_type != ET_CORE) {
             if (program_header.p_type == PT_LOAD && program_header.p_align == 0) {
                 if (verbose)