[LyX/master] Fix make dist

[Jean-Marc Lasgouttes]

commit cede08451e604241d3af7a540ff3623abe3c0a9f
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Sat Nov 28 23:43:06 2020 +0100

    Fix make dist
---
 3rdparty/boost/Makefile.am |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/3rdparty/boost/Makefile.am b/3rdparty/boost/Makefile.am
index bd4a2dd..ff8fa4b 100644
--- a/3rdparty/boost/Makefile.am
+++ b/3rdparty/boost/Makefile.am
@@ -5,9 +5,7 @@ EXTRA_DIST = boost \
 	LICENSE_1_0.txt \
 	libs/CMakeLists.txt \
 	libs/regex/CMakeLists.txt \
-	libs/regex/src/CMakeLists.txt \
-	libs/regex/src/usinstances.cpp
-# The last file above is only compiled for msvc (see cmake)
+	libs/regex/src/CMakeLists.txt
 
 AM_CPPFLAGS += -DBOOST_USER_CONFIG="<config.h>" 
 AM_CPPFLAGS +=  $(BOOST_INCLUDES)