Meson build system: misc adjustements for documentation

doc/meson.build

-latexmk = find_program('latexmk')
+latexmk_exe = find_program('latexmk')
 
 # We have to set TEXINPUTS because the current directory is not the source
 # directory when latexmk is invoked (and using the -cd option in combination
@@ -8,6 +8,8 @@ latexmk = find_program('latexmk')
 # Without the -g flag, latexmk remembers a previous build failure and will refuse
 # to recompile even if the error has been fixed in the TeX source
 
+latexmk_command = [ latexmk_exe, '-pdf', '-g', '-outdir=@OUTDIR@', '-auxdir=@PRIVATE_DIR@', '@INPUT@']
+
 # The \graphicspath{} command does not compute directories relative to TEXINPUTS,
 # so add these manually
 logos_dir = meson.current_source_dir() / 'logos'
@@ -15,15 +17,19 @@ logos_dir = meson.current_source_dir() / 'logos'
 custom_target('macroprocessor.pdf',
               output : 'macroprocessor.pdf',
               input : 'macroprocessor/macroprocessor.tex',
-              command : [ latexmk, '-pdf', '-g', '-outdir=@OUTDIR@', '-auxdir=@PRIVATE_DIR@', '@INPUT@'],
+              command : latexmk_command,
               env : { 'TEXINPUTS': meson.current_source_dir() + '/macroprocessor:' + logos_dir + ':' },
+              depend_files : [ 'macroprocessor/new-design.pdf', 'logos/dlogo.png' ],
               install : true,
               install_dir : 'share/doc/dynare')
 
 custom_target('preprocessor.pdf',
               output : 'preprocessor.pdf',
               input : 'preprocessor/preprocessor.tex',
-              command : [ latexmk, '-pdf', '-g', '-outdir=@OUTDIR@', '-auxdir=@PRIVATE_DIR@', '@INPUT@'],
+              command : latexmk_command,
               env : { 'TEXINPUTS': meson.current_source_dir() + '/preprocessor:' + logos_dir + ':' },
+              depend_files : [ 'preprocessor/expr.png', 'preprocessor/expr-sharing.png',
+                               'preprocessor/json-preprocessor.png', 'preprocessor/matrices.png',
+                               'preprocessor/overview.png', 'logos/dlogo.png' ],
               install : true,
               install_dir : 'share/doc/dynare')