[LyX/master] Avoid python based lilypond-book detection if it's not needed - e.g. on Mac

[Stephan Witt]

commit 6372f5569e4d6747642f7cbb0fa6e4eac2deab69
Author: Stephan Witt <switt at lyx.org>
Date:   Fri Dec 31 11:54:14 2021 +0100

    Avoid python based lilypond-book detection if it's not needed - e.g. on Mac
---
 lib/configure.py |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/lib/configure.py b/lib/configure.py
index 68bdc09..bddb94c 100644
--- a/lib/configure.py
+++ b/lib/configure.py
@@ -1330,6 +1330,11 @@ def checkConverterEntries():
                     addToRC(r'\copier docbook5 "python $$s/scripts/docbook_copy.py ' + docbook_lilypond_cmd.replace('"', r'\"') + r' $$i $$o"')
 
                     logger.info('+  found LilyPond-book version %s.' % version_number)
+
+                    # early exit on first match, avoid 2nd try with problematic python call
+                    # 1) in case of configure.py called with "python3" hardcoded "python" call is wrong
+                    # 2) in case of lilypond-book being an executable or shell script the python call is useless
+                    break
                 else:
                     logger.info('+  found LilyPond-book, but version %s is too old.' % version_number)
         if not found_lilypond_book: