[llvm-strings] Remove use of hard coded executable name

[gbreynoo]

Summary

Other tools take their tool name from argv[0] for use in output messages. This change makes llvm-strings consistent with other tools rather than using a hard coded value.

[MaskRay]

Looks great!

llvm/test/tools/llvm-strings/help.test

 ## Show that help text is printed correctly when requested.
 
 RUN: llvm-strings -h | FileCheck %s
 RUN: llvm-strings --help | FileCheck %s
 
 CHECK: OVERVIEW: llvm string dumper
-CHECK: USAGE: llvm-strings [options] <input object files>{{$}}
+CHECK: USAGE: {{.*}}llvm-strings{{(.exe)?}} [options] <input object files>{{$}}
 CHECK: OPTIONS:
 CHECK:   --all
 CHECK:   -a
 CHECK: Pass @FILE as argument to read options from FILE.

llvm/test/tools/llvm-strings/length.test

 
 ## Show --bytes works too.
 RUN: llvm-strings --bytes 2 %t | FileCheck --check-prefix CHECK-2 %s --implicit-check-not={{.}}
 
 ## Show different syntaxes work.
 RUN: llvm-strings --bytes=2 %t | FileCheck --check-prefix CHECK-2 %s --implicit-check-not={{.}}
 RUN: llvm-strings -n 2 %t | FileCheck --check-prefix CHECK-2 %s --implicit-check-not={{.}}
 
-CHECK-0: llvm-strings: error: expected a positive integer, but got '0'
+CHECK-0: error: expected a positive integer, but got '0'
 
 CHECK-1:      a
 CHECK-1-NEXT: ab
 CHECK-1-NEXT: abc
 CHECK-1-NEXT: abcd
 CHECK-1-NEXT: abcde
 
 CHECK-2:      ab
 CHECK-2-NEXT: abc
 CHECK-2-NEXT: abcd
 CHECK-2-NEXT: abcde
 
 CHECK-4:      abcd
 CHECK-4-NEXT: abcde
 
 CHECK-5:      abcde
 
 ## Show that a non-numeric argument is rejected.
 RUN: not llvm-strings -n foo %t 2>&1 | FileCheck %s --check-prefix=ERR
-ERR: llvm-strings: error: expected a positive integer, but got 'foo'
+ERR: error: expected a positive integer, but got 'foo'

llvm/test/tools/llvm-strings/radix.test

 CHECK-HEX: {{^}}      e four
 CHECK-HEX: {{^}}     13 five
 CHECK-HEX: {{^}}     1c seven
 CHECK-HEX: {{^}}     22 eight
 CHECK-HEX: {{^}}     28 nine
 
 ## Show that an invalid value is rejected.
 RUN: not llvm-strings --radix z %t/a.txt 2>&1 | FileCheck %s --check-prefix=INVALID
-INVALID: llvm-strings: error: --radix value should be one of: '' (no offset), 'o' (octal), 'd' (decimal), 'x' (hexadecimal)
+INVALID: error: --radix value should be one of: '' (no offset), 'o' (octal), 'd' (decimal), 'x' (hexadecimal)

llvm/tools/llvm-strings/llvm-strings.cpp

 };
 
 class StringsOptTable : public opt::OptTable {
 public:
   StringsOptTable() : OptTable(InfoTable) { setGroupedShortOptions(true); }
 };
 } // namespace
 
-const char ToolName[] = "llvm-strings";
+static StringRef ToolName;
 
 static cl::list<std::string> InputFileNames(cl::Positional,
                                             cl::desc("<input object files>"),
                                             cl::ZeroOrMore);
 
 static int MinLength = 4;
 static bool PrintFileName;
 
if (S)
     print(S - B, StringRef(S, E - S));
 }
 
 int main(int argc, char **argv) {
   InitLLVM X(argc, argv);
   BumpPtrAllocator A;
   StringSaver Saver(A);
   StringsOptTable Tbl;
+  ToolName = argv[0];
   opt::InputArgList Args =
       Tbl.parseArgs(argc, argv, OPT_UNKNOWN, Saver,
                     [&](StringRef Msg) { reportCmdLineError(Msg); });
   if (Args.hasArg(OPT_help)) {
     Tbl.printHelp(
         outs(),
         (Twine(ToolName) + " [options] <input object files>").str().c_str(),
         "llvm string dumper");