Improve error message when run on statically linked binaries

If .dynamic, .dynstr or .interp sections aren't found, give an extra hint
to the user that the input file is statically linked.

Author: dezgeg

src/patchelf.cc

@@ -557,8 +557,12 @@ template<ElfFileParams>
 Elf_Shdr & ElfFile<ElfFileParamNames>::findSection(const SectionName & sectionName)
 {
     Elf_Shdr * shdr = findSection2(sectionName);
-    if (!shdr)
-        error("cannot find section '" + sectionName + "'");
+    if (!shdr) {
+        std::string extraMsg = "";
+        if (sectionName == ".interp" || sectionName == ".dynamic" || sectionName == ".dynstr")
+            extraMsg = ". The input file is most likely statically linked";
+        error("cannot find section '" + sectionName + "'" + extraMsg);
+    }
     return *shdr;
 }