[BlockExtractor] Change the basic block separator from ',' to ';'

[qcolombet]

Summary

This change aims at making the file format be compatible with the
way LLVM handles command line options.

[volkan]

LGTM

lib/Transforms/IPO/BlockExtractor.cpp

Buf->getBuffer().split(Lines, '\n', /*MaxSplit=*/-1,
                          /*KeepEmpty=*/false);
   for (const auto &Line : Lines) {
     SmallVector<StringRef, 4> LineSplit;
     Line.split(LineSplit, ' ', /*MaxSplit=*/-1,
                /*KeepEmpty=*/false);
     if (LineSplit.empty())
       continue;
     SmallVector<StringRef, 4> BBNames;
-    LineSplit[1].split(BBNames, ',', /*MaxSplit=*/-1,
+    LineSplit[1].split(BBNames, ';', /*MaxSplit=*/-1,
                        /*KeepEmpty=*/false);
     if (BBNames.empty())
       report_fatal_error("Missing bbs name");
     BlocksByName.push_back({LineSplit[0], {BBNames.begin(), BBNames.end()}});
   }
 }
 
 /// Extracts the landing pads to make sure all of them have only one

test/Transforms/BlockExtractor/extract-blocks-with-groups.ll

 ; Extract the 'if', 'then', and 'else' blocks into the same function.
-; RUN: echo 'foo if,then,else' > %t
+; RUN: echo 'foo if;then;else' > %t
 ; Make sure we can still extract a single basic block
 ; RUN: echo 'foo end' >> %t
-; RUN: echo 'bar bb14,bb20' >> %t
+; RUN: echo 'bar bb14;bb20' >> %t
 ; RUN: opt -S -extract-blocks -extract-blocks-file=%t %s | FileCheck %s
 
 ; CHECK-LABEL: foo
 ;
 ; CHECK: if:
 ; The diamond will produce an i32 value, make sure we account for that.
 ; CHECK: [[RES_VAL_ADDR:%[^ ]*]] = alloca i32
 ; CHECK-NEXT: br label %[[FOO_DIAMOND_LABEL:.*$]]