[vcpkg] Apply fixes needed to extract vcpkg-tool (#16012)

utilities.cmake: Disable warnings that are firing on Azure Pipelines CI machines due to different Clang version.

expected.h: Fix a bug I introduced in https://github.com/microsoft/vcpkg/pull/15638/ because I was under the impression expected worked like optional (in that value_or_exit for it should be treated as a program bug)

build.cpp: Add (void)s to silence warnings.

binarycaching.cpp: Repair assumption that the current directory is C: which isn't true on the Hosted Azure Pipelines agents.

others: Make unit tests respect %VCPKG_ROOT%, as necessary in the vcpkg_tool repo. Note that this required splitting vcpkgcmdarguments::ImbueFromEnvironment into the once-only process modifying part and the just imbue from environment part.

2 files changed, 5 insertions, 3 deletions

diff --git a/toolsrc/include/vcpkg/base/expected.h b/toolsrc/include/vcpkg/base/expected.h
index 13e70057d..f24366c4a 100644
--- a/toolsrc/include/vcpkg/base/expected.h
+++ b/toolsrc/include/vcpkg/base/expected.h
@@ -229,7 +229,7 @@ namespace vcpkg
             if (m_s.has_error())
             {
                 System::print2(System::Color::error, m_s.to_string(), "\n");
-                Checks::unreachable(line_info);
+                Checks::exit_fail(line_info);
             }
         }
 
diff --git a/toolsrc/include/vcpkg/vcpkgcmdarguments.h b/toolsrc/include/vcpkg/vcpkgcmdarguments.h
index 365f892a0..14208e926 100644
--- a/toolsrc/include/vcpkg/vcpkgcmdarguments.h
+++ b/toolsrc/include/vcpkg/vcpkgcmdarguments.h
@@ -212,7 +212,6 @@ namespace vcpkg
         }
 
         bool output_json() const { return json.value_or(false); }
-        bool is_recursive_invocation() const { return m_is_recursive_invocation; }
 
         std::string command;
         std::vector<std::string> command_arguments;
@@ -221,13 +220,16 @@ namespace vcpkg
 
         void imbue_from_environment();
 
+        // Applies recursive settings from the environment or sets a global environment variable
+        // to be consumed by subprocesses; may only be called once per process.
+        static void imbue_or_apply_process_recursion(VcpkgCmdArguments& args);
+
         void check_feature_flag_consistency() const;
 
         void debug_print_feature_flags() const;
         void track_feature_flag_metrics() const;
 
     private:
-        bool m_is_recursive_invocation = false;
         std::unordered_set<std::string> command_switches;
         std::unordered_map<std::string, std::vector<std::string>> command_options;
     };