Don't set WINEPREFIX for the current process

`native_environment` allows modification of the current process's
environment, so we had to use the plain `environment` class instead.

CHANGELOG.md

@@ -24,6 +24,9 @@ Versioning](https://semver.org/spec/v2.0.0.html).
   the same name from being used simultaneously in multiple Wine prefixes.
 - Fixed manual Wine prefix overides through the `WINEPREFIX` environment
   variable not being reflected in the output shwon in startup.
+- Fixed the Wine prefix being overwritten for all subsequent plugins opened
+  within the same process. This prevented the use of multiple Wine prefixes
+  within hosts that do not sandbox their plugins, such as Ardour.
 
 ## [1.2.0] - 2020-05-29
 

src/plugin/plugin-bridge.cpp

@@ -597,7 +597,7 @@ void PluginBridge::log_init_message() {
 
     // If the Wine prefix is manually overridden, then this should be made
     // clear. This follows the behaviour of `set_wineprefix()`.
-    bp::native_environment env = boost::this_process::environment();
+    bp::environment env = boost::this_process::environment();
     if (!env["WINEPREFIX"].empty()) {
         init_msg << env["WINEPREFIX"].to_string() << " <overridden>";
     } else {

src/plugin/utils.cpp

@@ -242,7 +242,7 @@ std::string get_wine_version() {
     // used to run Wine, so will will respect this as well
     std::string wine_command = "wine";
 
-    bp::native_environment env = boost::this_process::environment();
+    bp::environment env = boost::this_process::environment();
     if (!env["WINELOADER"].empty()) {
         wine_command = env.get("WINELOADER");
     }
@@ -271,7 +271,7 @@ std::string get_wine_version() {
 }
 
 bp::environment set_wineprefix() {
-    bp::native_environment env = boost::this_process::environment();
+    bp::environment env = boost::this_process::environment();
 
     // Allow the wine prefix to be overridden manually
     if (!env["WINEPREFIX"].empty()) {