[tools] Fix missing executable permission on downloaded tools for Unix

include/vcpkg/base/files.h

@@ -334,6 +334,8 @@ namespace vcpkg
 
         virtual bool last_write_time(DiagnosticContext& context, const Path& target, int64_t new_time) const = 0;
 
+        virtual bool set_executable(DiagnosticContext& context, const Path& target) const = 0;
+
         using ReadOnlyFilesystem::current_path;
         virtual void current_path(const Path& new_current_path, std::error_code&) const = 0;
         void current_path(const Path& new_current_path, LineInfo li) const;

src/vcpkg/base/files.cpp

@@ -4051,6 +4051,31 @@ namespace vcpkg
 #endif // ^^^ !_WIN32
         }
 
+        virtual bool set_executable(DiagnosticContext& context, const Path& target) const override
+        {
+#if defined(_WIN32)
+            // On Windows, executability is determined by file extension, not permissions.
+            (void)context;
+            (void)target;
+            return true;
+#else  // ^^^ _WIN32 // !_WIN32 vvv
+            if (::chmod(target.c_str(), 0755) != 0)
+            {
+                auto local_errno = errno;
+                context.report(
+                    DiagnosticLine{DiagKind::Error,
+                                   target,
+                                   msg::format(msgSystemApiErrorMessage,
+                                               msg::system_api = "chmod",
+                                               msg::exit_code = local_errno,
+                                               msg::error_msg = std::generic_category().message(local_errno))});
+                return false;
+            }
+
+            return true;
+#endif // ^^^ !_WIN32
+        }
+
         virtual void write_contents(const Path& file_path, StringView data, std::error_code& ec) const override
         {
             StatsTimer t(g_us_filesystem_stats);
@@ -4494,6 +4519,19 @@ namespace vcpkg
             return false;
         }
 
+        bool set_executable(DiagnosticContext& context, const Path&) const override
+        {
+            context.report_system_error("set_executable",
+#if defined(_WIN32)
+                                        ERROR_NOT_SUPPORTED
+#else
+                                        ENOTSUP
+#endif
+            );
+
+            return false;
+        }
+
         void current_path(const Path&, std::error_code& ec) const override { assign_not_supported(ec); }
 
         std::unique_ptr<IExclusiveFileLock> take_exclusive_file_lock(DiagnosticContext& context,

src/vcpkg/tools.cpp

@@ -1052,6 +1052,7 @@ namespace vcpkg
                 return nullopt;
             }
 
+            fs.set_executable(context, exe_path);
             return exe_path;
         }