GitHub CI Win: Version.txt is not present in NDI

Windows distribution of NDI usually doesn't contain Version.txt so do
not use it. Moreover the previous way of creating the version file (in
.bashrc) was not perfect.

Write at least NDI major version if NDI_VERSION is not present.

.github/scripts/Windows/prepare_msys.sh

@@ -1,4 +1,6 @@
-#!/bin/sh -eux
+#!/bin/bash
+
+set -ex
 
 mkdir -p /usr/local/lib /usr/local/bin /usr/local/include
 cat >> ~/.bash_profile <<'EOF'
@@ -17,7 +19,6 @@ if test -d /c/Program\ Files/NDI; then
         NDI_D=$(ls -d /c/Program\ Files/NDI/*SDK)
         export CPATH=$CPATH:$NDI_D/Include
         export LIBRARY_PATH=$LIBRARY_PATH:$NDI_D/Lib/x64
-        cat $NDI_D/Version.txt | sed 's/\(.*\)/\#define NDI_VERSION \"\1\"/' | tee /usr/local/include/ndi_version.h
 fi
 
 JACK_D=/c/Program\ Files/JACK2

src/video_capture/ndi.cpp

@@ -167,6 +167,8 @@ static void show_help(struct vidcap_state_ndi *s) {
         s->NDIlib->find_destroy(pNDI_find);
 #ifdef NDI_VERSION
         cout << NDI_VERSION "\n";
+#elif defined USE_NDI_VERSION
+        cout << "NDI version " << USE_NDI_VERSION << "\n";
 #endif
 }