LibCore: Don't use execvpe on Solaris

Userland/Libraries/LibCore/System.cpp

@@ -1197,7 +1197,7 @@ ErrorOr<void> exec(StringView filename, ReadonlySpan<StringView> arguments, Sear
         envp[environment->size()] = nullptr;
 
         if (search_in_path == SearchInPath::Yes && !filename.contains('/')) {
-#    if defined(AK_OS_MACOS) || defined(AK_OS_FREEBSD)
+#    if defined(AK_OS_MACOS) || defined(AK_OS_FREEBSD) || defined(AK_OS_SOLARIS)
             // These BSDs don't support execvpe(), so we'll have to manually search the PATH.
             ScopedValueRollback errno_rollback(errno);