Don't put -dev version numbers in platformio library.json

See https://github.com/nanopb/nanopb/commit/cc74b9f200176edc5524aa00ba45fa90a5e87d27 for discussion.

library.json

 {
   "name": "Nanopb",
-  "version": "0.3.9-dev",
+  "version": "0.3.8",
   "keywords": "protocol buffers, protobuf, google",
   "description": "Nanopb is a plain-C implementation of Google's Protocol Buffers data format. It is targeted at 32 bit microcontrollers, but is also fit for other embedded systems with tight (2-10 kB ROM, <1 kB RAM) memory constraints.",
   "repository": {

tools/set_version.sh

@@ -9,5 +9,6 @@ sed -i -e 's/#define\s*NANOPB_VERSION\s*.*/#define NANOPB_VERSION '$1'/' pb.h
 sed -i -e 's/set(\s*nanopb_VERSION_STRING\s*[^)]*)/set(nanopb_VERSION_STRING '$1')/' CMakeLists.txt
 
 VERSION_ONLY=$(echo $1 | sed 's/nanopb-//')
-sed -i -e 's/"version":\s*"[^"]*"/"version": "'$VERSION_ONLY'"/' library.json
-
+if [[ $1 != *dev ]]
+then sed -i -e 's/"version":\s*"[^"]*"/"version": "'$VERSION_ONLY'"/' library.json
+fi