fix adjusting startPage

startPage is adjusted unconditionally for all executables.
This results in incorrect addresses assigned to INTERP and LOAD
program headers, which breaks patched executable.

Adjusting startPage variable only when startOffset > startPage
should fix this.

This change is related to the issue NixOS#10

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>

src/patchelf.cc

@@ -630,10 +630,8 @@ void ElfFile<ElfFileParamNames>::rewriteSectionsLibrary()
        since DYN executables tend to start at virtual address 0, so
        rewriteSectionsExecutable() won't work because it doesn't have
        any virtual address space to grow downwards into. */
-    if (isExecutable) {
-        if (startOffset >= startPage) {
-            debug("shifting new PT_LOAD segment by %d bytes to work around a Linux kernel bug\n", startOffset - startPage);
-        }
+    if (isExecutable && startOffset > startPage) {
+        debug("shifting new PT_LOAD segment by %d bytes to work around a Linux kernel bug\n", startOffset - startPage);
         startPage = startOffset;
     }