[vcpkg] Use CreateProcess on Windows. Improve EnvVars manipulation and handling. (#9897)

* [vcpkg] Rewrite process spawning on windows to always use CreateProcess, enabling better environment handling

* [vcpkg] Use environment cache to avoid calling vcvars multiple times

* [vcpkg] Increase buffer size while computing hashes

* [vcpkg] Remove unneeded cmd.exe wrapper process on all CreateProcess calls

* [vcpkg] Fix .vcxproj{,.filters}

* [vcpkg] Upgrade Ctrl-C state machine to handle multiple background processes.

* [vcpkg] Fix regression while launching metrics: 'start' can't be passed directly to CreateProcessW

* [vcpkg] Fix typo on non-Windows

* [vcpkg] Fix various uses of >NUL across the code

* [vcpkg] Fix various uses of >NUL across the code

2 files changed, 26 insertions, 5 deletions

diff --git a/toolsrc/include/vcpkg/base/checks.h b/toolsrc/include/vcpkg/base/checks.h
index 3c0c073d2..519ca58f4 100644
--- a/toolsrc/include/vcpkg/base/checks.h
+++ b/toolsrc/include/vcpkg/base/checks.h
@@ -8,6 +8,9 @@ namespace vcpkg::Checks
 {
     void register_global_shutdown_handler(void (*func)());
 
+    // Note: for internal use
+    [[noreturn]] void final_cleanup_and_exit(const int exit_code);
+
     // Indicate that an internal error has occurred and exit the tool. This should be used when invariants have been
     // broken.
     [[noreturn]] void unreachable(const LineInfo& line_info);
diff --git a/toolsrc/include/vcpkg/base/system.process.h b/toolsrc/include/vcpkg/base/system.process.h
index 14e2eb109..b2e76ff74 100644
--- a/toolsrc/include/vcpkg/base/system.process.h
+++ b/toolsrc/include/vcpkg/base/system.process.h
@@ -3,6 +3,7 @@
 #include <vcpkg/base/files.h>
 #include <vcpkg/base/zstringview.h>
 
+#include <functional>
 #include <string>
 #include <unordered_map>
 #include <vector>
@@ -30,17 +31,34 @@ namespace vcpkg::System
         std::string output;
     };
 
-    int cmd_execute_clean(const ZStringView cmd_line,
-                          const std::unordered_map<std::string, std::string>& extra_env = {},
-                          const std::string& prepend_to_path = {});
+    struct Environment
+    {
+#if defined(_WIN32)
+        std::wstring m_env_data;
+#endif
+    };
 
-    int cmd_execute(const ZStringView cmd_line);
+    const Environment& get_clean_environment();
+    Environment get_modified_clean_environment(const std::unordered_map<std::string, std::string>& extra_env,
+                                               const std::string& prepend_to_path = {});
+
+    int cmd_execute(const ZStringView cmd_line, const Environment& env = {});
+    int cmd_execute_clean(const ZStringView cmd_line);
 
 #if defined(_WIN32)
+    Environment cmd_execute_modify_env(const ZStringView cmd_line, const Environment& env = {});
+
     void cmd_execute_no_wait(const StringView cmd_line);
 #endif
 
-    ExitCodeAndOutput cmd_execute_and_capture_output(const ZStringView cmd_line);
+    ExitCodeAndOutput cmd_execute_and_capture_output(const ZStringView cmd_line, const Environment& env = {});
+
+    int cmd_execute_and_stream_lines(const ZStringView cmd_line,
+                                     std::function<void(const std::string&)> per_line_cb,
+                                     const Environment& env = {});
 
+    int cmd_execute_and_stream_data(const ZStringView cmd_line,
+                                    std::function<void(StringView)> data_cb,
+                                    const Environment& env = {});
     void register_console_ctrl_handler();
 }