[C++] Ignore recursive marker in recipes

Test case:

$ cat Makefile.recursive
.PHONY: default
default:
        +echo DONE

$ ckati --warn --gen_all_targets --regen --ninja -f Makefile.recursive
Makefile.recursive was modified, regenerating...
$ fgrep DONE build.ninja
 command = /bin/sh -c "+echo DONE"

$ ninja
[1/1] build default
FAILED: default
/bin/sh -c "+echo DONE"
/bin/sh: + : invalid option
Usage:  /bin/sh [GNU long option] [option] ...
...

Fixes https://github.com/google/kati/issues/57

Change-Id: Ic40d71ff2b168158661eb2eac638adaeadaec1fe

1 files changed, 2 insertions, 0 deletions

diff --git a/command.cc b/command.cc
index f75a8a0..8907630 100644
--- a/command.cc
+++ b/command.cc
@@ -160,6 +160,8 @@ void ParseCommandPrefixes(StringPiece* s, bool* echo, bool* ignore_error) {
       *echo = false;
     } else if (c == '-') {
       *ignore_error = true;
+    } else if (c == '+') {
+      // ignore recursion marker
     } else {
       break;
     }