fix windows build

.travis.yml

@@ -25,7 +25,7 @@ before_install:
       export msys2+='& C:\\tools\\msys64\\msys2_shell.cmd -defterm -no-start'
       export mingw64="$msys2 -mingw64 -full-path -here -c \$\* --"
       export msys2+=" -msys2 -c \$\* --"
-      $msys2 pacman --sync --noconfirm --needed mingw-w64-x86_64-toolchain mingw-w64-x86_64-librsvg mingw-w64-x86_64-meson mingw-w64-x86_64-libsndfile guile
+      $msys2 pacman --sync --noconfirm --needed mingw-w64-x86_64-toolchain mingw-w64-x86_64-librsvg mingw-w64-x86_64-meson mingw-w64-x86_64-libsndfile guile mingw-w64-x86_64-make
       ## Install more MSYS2 packages from https://packages.msys2.org/base here
       taskkill //IM gpg-agent.exe //F || true # https://travis-ci.community/t/4967
       export PATH=/C/tools/msys64/mingw64/bin:$PATH
@@ -35,7 +35,7 @@ before_install:
       brew update
       # use || true because it returns 1
       brew install meson libsndfile librsvg guile || true
-      brew link --overwrite python
+      brew link --overwrite python || true
       ;;
     linux)
       sudo apt-get install -y librsvg2-dev libjack-dev libsndfile1-dev ninja-build python3 git lcov guile-2.0 lv2-dev

plugins/manifest_gen.scm

@@ -1,5 +1,3 @@
-#!@GUILE@ -s
-!#
 ;;;
 ;;; Copyright (C) 2020 Alexandros Theodotou <alex at zrythm dot org>
 ;;;

plugins/manifest_gen_wrap.sh

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+
+cd @CURRENT_SOURCE_DIR@
+@GUILE@ -s manifest_gen.scm "$@"

plugins/meson.build

@@ -42,6 +42,19 @@ else
   libext = '.so'
 endif
 
+guile_path = guile.path ()
+if os_windows
+  guile_path = 'guile'
+endif
+manifest_gen_wrap = configure_file (
+  input: 'manifest_gen_wrap.sh',
+  output: 'manifest_gen_wrap.sh',
+  configuration: {
+    'CURRENT_SOURCE_DIR': meson.current_source_dir(),
+    'GUILE': guile_path,
+    },
+  )
+
 foreach pl : plugins
 if get_option ('plugins').contains (pl[0])
 
@@ -205,10 +218,9 @@ if get_option ('plugins').contains (pl[0])
 
   # create and install manifest ttl
   manifest_ttl = configure_file (
-    input: 'manifest_gen.scm',
     output: pl_str + '_manifest.ttl',
     command: [
-      guile, '-s', '@INPUT@', '@OUTPUT@',
+      manifest_gen_wrap, '@OUTPUT@',
       project_uri, pl_type, pl_uri,
       pl_dsp_binary, pl_minor_version,
       pl_micro_version, pl_ttl,