fix: Don't supress stderr anymore (#1822)

### Problem description

Typing `--help` causes ImHex to exit without outputting anything.
Diagnostic messages from glib, ASan, other libraries that might have
something important to say, etc. are also suppressed.

### Implementation description

This effectively reverts 7c1e33d, which
was partially reverted only on Windows by code that was left commented
out in f114239.

Allowing other libraries to print to stderr may make the output ‘ugly’,
but lots of things print to stderr that are important for figuring out
why something is bugged, like ASan and glib.

### Additional things


![image](https://github.com/user-attachments/assets/fa6771e2-da2e-45ea-93cd-06c3f6bfd3bf)

main/gui/source/window/linux_window.cpp

@@ -14,7 +14,6 @@
     #include <wolv/utils/core.hpp>
 
     #include <nlohmann/json.hpp>
-    #include <cstdio>
     #include <sys/wait.h>
     #include <unistd.h>
 
@@ -137,11 +136,6 @@ namespace hex {
                 setenv("LD_LIBRARY_PATH", hex::format("{};{}", hex::getEnvironmentVariable("LD_LIBRARY_PATH").value_or(""), path.string().c_str()).c_str(), true);
         }
 
-        // Various libraries sadly directly print to stderr with no way to disable it
-        // We redirect stderr to /dev/null to prevent this
-        wolv::util::unused(freopen("/dev/null", "w", stderr));
-        setvbuf(stderr, nullptr, _IONBF, 0);
-
         // Redirect stdout to log file if we're not running in a terminal
         if (!isatty(STDOUT_FILENO)) {
             log::impl::redirectToFile();

main/gui/source/window/macos_window.cpp

@@ -11,7 +11,6 @@
     #include <hex/helpers/logger.hpp>
     #include <hex/helpers/default_paths.hpp>
 
-    #include <cstdio>
     #include <unistd.h>
 
     #include <imgui_impl_glfw.h>
@@ -41,11 +40,6 @@ namespace hex {
                 setenv("LD_LIBRARY_PATH", hex::format("{};{}", hex::getEnvironmentVariable("LD_LIBRARY_PATH").value_or(""), path.string().c_str()).c_str(), true);
         }
 
-        // Various libraries sadly directly print to stderr with no way to disable it
-        // We redirect stderr to /dev/null to prevent this
-        freopen("/dev/null", "w", stderr);
-        setvbuf(stderr, nullptr, _IONBF, 0);
-
         // Redirect stdout to log file if we're not running in a terminal
         if (!isatty(STDOUT_FILENO)) {
             log::impl::redirectToFile();

main/gui/source/window/win_window.cpp

@@ -29,8 +29,6 @@
     #include <shellapi.h>
     #include <timeapi.h>
 
-    #include <cstdio>
-
 namespace hex {
 
     template<typename T>
@@ -422,12 +420,6 @@ namespace hex {
             reopenConsoleHandle(STD_INPUT_HANDLE,  STDIN_FILENO,  stdin);
             reopenConsoleHandle(STD_OUTPUT_HANDLE, STDOUT_FILENO, stdout);
 
-            // Explicitly don't forward stderr because some libraries like to write to it
-            // with no way to disable it (e.g., libmagic)
-            /*
-                reopenConsoleHandle(STD_ERROR_HANDLE,  STDERR_FILENO, stderr);
-            */
-
             // Enable ANSI colors in the console
             log::impl::enableColorPrinting();
         } else {