Bump Swift version in build_podspec.sh (#294)

Motivation:

SwiftNIO recently dropped support for Swift 5.0 and Swift 5.1 but our
build_podspec.sh script doesn't reflect this change. Additionally the
list_topsorted_dependencies.sh script always assumed named depenencies
when listing module depenencies. Since our tools version has now been
bumped to 5.2 that's no longer the case and the script produces a bunch
of nulls which throws the build_podspec.sh script off course.

Modifications:

- Bump the Swift version in build_podspec.sh to 5.2
- Include "product" dependencies when listing module dependencies in
  list_topsorted_dependencies.sh

Result:

Podspecs are created as expected

scripts/build_podspec.sh

@@ -102,7 +102,7 @@ Pod::Spec.new do |s|
   s.documentation_url = 'https://apple.github.io/swift-nio-http2/'
   s.module_name = '${target#Swift}'
 
-  s.swift_version = '5.0'
+  s.swift_version = '5.2'
   s.cocoapods_version = '>=1.6.0'
   s.ios.deployment_target = '10.0'
   s.osx.deployment_target = '10.12'

scripts/list_topsorted_dependencies.sh

@@ -60,7 +60,7 @@ fi
 
 if [[ ! -z "$module_dependency" ]]; then
   swift package dump-package | jq -r ".targets |
-                                      map(select(.name == \"$module_dependency\" and .type == \"regular\") | .dependencies | map(.byName | first)) | .[] | .[]"
+                                      map(select(.name == \"$module_dependency\" and .type == \"regular\") | .dependencies | map(.byName | first) + map(.product | first) ) | del(.[][] | nulls) | .[] | .[]"
   exit 0
 fi
 
@@ -89,4 +89,4 @@ swift package dump-package | jq '.targets |
 done
 )
 
-rm "$tmpfile"
+rm "$tmpfile"