Reason: Fix compilation on musl
Upstream: No

Got it from Void Linux:
https://github.com/void-linux/void-packages/commit/427d50c6a66e4a1338dbe230a41b98a2419116a9

--- a/src/CLI/usbguard.cpp
+++ b/src/CLI/usbguard.cpp
@@ -26,10 +26,8 @@
 #include <map>
 #include <iostream>
 
-#ifndef _GNU_SOURCE
-  #define _GNU_SOURCE
-#endif
-#include <cstring> /* GNU version of basename(3) */
+#include <cstring>
+#include <libgen.h>
 
 #include "usbguard.hpp"
 #include "usbguard-get-parameter.hpp"
@@ -99,7 +97,7 @@
 
   static int usbguard_cli(int argc, char* argv[])
   {
-    usbguard_arg0 = ::basename(argv[0]);
+    usbguard_arg0 = ::basename(strdup(argv[0]));
 
     if (argc == 1) {
       showTopLevelHelp();
--- a/src/CLI/usbguard-rule-parser.cpp
+++ b/src/CLI/usbguard-rule-parser.cpp
@@ -24,10 +24,8 @@
 #include "RuleParser.hpp"
 
 #include <iostream>
-#ifndef _GNU_SOURCE
-  #define _GNU_SOURCE
-#endif
 #include <cstring>
+#include <libgen.h>
 #include <fstream>
 
 #include <getopt.h>
@@ -43,8 +41,10 @@
 
 static void showHelp(std::ostream& stream, const char* usbguard_arg0)
 {
-  stream << " Usage: " << ::basename(usbguard_arg0) << " [OPTIONS] <rule_spec>" << std::endl;
-  stream << " Usage: " << ::basename(usbguard_arg0) << " [OPTIONS] -f <file>" << std::endl;
+  char *usbguard_arg0_copy = strdup(usbguard_arg0);
+  stream << " Usage: " << ::basename(usbguard_arg0_copy) << " [OPTIONS] <rule_spec>" << std::endl;
+  stream << " Usage: " << ::basename(usbguard_arg0_copy) << " [OPTIONS] -f <file>" << std::endl;
+  free(usbguard_arg0_copy);
   stream << std::endl;
   stream << " Options:" << std::endl;
   stream << "  -f, --file       Interpret the argument as a path to a file that should be parsed." << std::endl;
--- a/src/DBus/gdbus-server.cpp
+++ b/rc/DBus/gdbus-server.cpp
@@ -23,6 +23,7 @@
 #include <stdlib.h>
 #include <iostream>
 #include <getopt.h>
+#include <libgen.h>
 #include "DBusBridge.hpp"
 
 static usbguard::DBusBridge* dbus_bridge = nullptr;
@@ -208,7 +209,9 @@
 
 static void showHelp(std::ostream& stream)
 {
-  stream << " Usage: " << ::basename(usbguard_arg0) << " [OPTIONS]" << std::endl;
+  char *usbguard_arg0_copy = strdup(usbguard_arg0);
+  stream << " Usage: " << ::basename(usbguard_arg0_copy) << " [OPTIONS]" << std::endl;
+  free(usbguard_arg0_copy);
   stream << std::endl;
   stream << " Options:" << std::endl;
   stream << "  -s, --system   Listen on the system bus." << std::endl;
--- a/src/Library/public/usbguard/Exception.hpp
+++ b/src/Library/public/usbguard/Exception.hpp
@@ -116,7 +116,8 @@
     static std::string reasonFromErrno(const int errno_value)
     {
       char buffer[1024];
-      return std::string(strerror_r(errno_value, buffer, sizeof buffer));
+      strerror_r(errno_value, buffer, sizeof buffer);
+      return std::string(buffer);
     }
   };