[LyX/2.4.x] Convert $${python} placeholder for graphic conversions

[José Matos]

commit cc75da1c3e109e4fd6b1305a707c70929000ddd6
Author: José Matos <jamatos at lyx.org>
Date:   Sun Apr 14 21:30:02 2024 +0100

    Convert $${python} placeholder for graphic conversions
    
    (cherry picked from commit cdcaf0e7b6cc45bc74175667c390c3148c4730e9)
---
 src/graphics/GraphicsConverter.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/graphics/GraphicsConverter.cpp b/src/graphics/GraphicsConverter.cpp
index 669f08d2ff..34d37a4066 100644
--- a/src/graphics/GraphicsConverter.cpp
+++ b/src/graphics/GraphicsConverter.cpp
@@ -362,6 +362,7 @@ static void build_script(string const & doc_fname,
 	string const token_base  = "$$b";
 	string const token_to    = "$$o";
 	string const token_todir = "$$d";
+	string const token_python = "$${python}";
 
 	EdgePath::const_iterator it  = edgepath.begin();
 	EdgePath::const_iterator end = edgepath.end();
@@ -405,6 +406,7 @@ static void build_script(string const & doc_fname,
 		command = subst(command, token_base,  "' + '\"' + infile_base + '\"' + '");
 		command = subst(command, token_to,    "' + '\"' + outfile + '\"' + '");
 		command = subst(command, token_todir, "' + '\"' + outdir + '\"' + '");
+		command = subst(command, token_python, os::python());
 
 		build_conversion_command(command, script);
 	}