Bug 1378986 - Adjust the fake phdr section properly. r=froydnj

The PT_PHDR segment is optional, but the Android toolchain decides to
create one in some cases, and places it first. When that happens, the
work around for bug 1233963 fails, because the fake phdr section has not
been adjusted yet (it only happens when we see a PT_LOAD).

So we adjust the fake phdr section when we see a PT_PHDR segment (and
avoid re-updating it when we see a subsequent PT_LOAD).

build/unix/elfhack/elf.cpp

@@ -228,6 +228,7 @@ Elf::Elf(std::ifstream &file)
     if (ehdr->e_phnum == 0)
         return;
 
+    bool adjusted_phdr_section = false;
     // Read program headers
     file.seekg(ehdr->e_phoff);
     for (int i = 0; i < ehdr->e_phnum; i++) {
@@ -247,12 +248,20 @@ Elf::Elf(std::ifstream &file)
         if ((phdr.p_type == PT_LOAD) && (phdr.p_offset == 0)) {
             // Use a fake section for ehdr and phdr
             ehdr->getShdr().sh_addr = phdr.p_vaddr;
-            phdr_section->getShdr().sh_addr += phdr.p_vaddr;
+            if (!adjusted_phdr_section) {
+                phdr_section->getShdr().sh_addr += phdr.p_vaddr;
+                adjusted_phdr_section = true;
+            }
             segment->addSection(ehdr);
             segment->addSection(phdr_section);
         }
-        if (phdr.p_type == PT_PHDR)
+        if (phdr.p_type == PT_PHDR) {
+            if (!adjusted_phdr_section) {
+                phdr_section->getShdr().sh_addr = phdr.p_vaddr;
+                adjusted_phdr_section = true;
+            }
             segment->addSection(phdr_section);
+        }
         for (int j = 1; j < ehdr->e_shnum; j++)
             if (phdr.contains(sections[j]))
                 segment->addSection(sections[j]);