Fix type comparison issue that is a hard error in GCC 10.

Taken from upstream:

  https://github.com/OpenTTD/grfcodec/commit/bb692b2c723c5e87cc8f89f445928e97594d5b8f

diff --git a/src/command.cpp b/src/command.cpp
index 9aa0e14..1f32cf1 100644
--- a/src/command.cpp
+++ b/src/command.cpp
@@ -300,8 +300,9 @@ bool parse_comment(const string&line){
 		break;
 	case BEAUTIFY:{
 		commandstream>>command_part;
-		uint val=find_command(command_part,beaut),togglebit;
-		if(val!=(uint)-1&&val!=OFF)_commandState.beautifier=true;
+		int val=find_command(command_part,beaut);
+		uint togglebit;
+		if(val!=-1&&val!=OFF)_commandState.beautifier=true;
 		switch(val){
 		case -1:
 			IssueMessage(0,COMMAND_INVALID_ARG,gen[BEAUTIFY].name);
@@ -372,7 +373,7 @@ bool parse_comment(const string&line){
 dotoggle:
 			commandstream>>command_part;
 			val=find_command(command_part,beaut);
-			if(!commandstream||val==(uint)-1){
+			if(!commandstream||val==-1){
 				IssueMessage(0,COMMAND_INVALID_ARG,gen[BEAUTIFY].name);
 				return true;
 			}
a href='/guix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=c573f92972b98cde7bfd7a2e0e484086074424dd'>refs</a><a class='active' href='/guix/log/etc/guix-daemon.conf.in'>log</a><a href='/guix/tree/etc/guix-daemon.conf.in?id=c573f92972b98cde7bfd7a2e0e484086074424dd'>tree</a><a href='/guix/commit/etc/guix-daemon.conf.in?id=c573f92972b98cde7bfd7a2e0e484086074424dd'>commit</a><a href='/guix/diff/etc/guix-daemon.conf.in?id=c573f92972b98cde7bfd7a2e0e484086074424dd'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/etc/guix-daemon.conf.in'>
<input type='hidden' name='id' value='c573f92972b98cde7bfd7a2e0e484086074424dd'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=c573f92972b98cde7bfd7a2e0e484086074424dd'>root</a>/<a href='/guix/log/etc?id=c573f92972b98cde7bfd7a2e0e484086074424dd'>etc</a>/<a href='/guix/log/etc/guix-daemon.conf.in?id=c573f92972b98cde7bfd7a2e0e484086074424dd'>guix-daemon.conf.in</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/etc/guix-daemon.conf.in?id=c573f92972b98cde7bfd7a2e0e484086074424dd&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2024-06-26 22:59:55 +0200'>2024-06-26</span></td><td><a href='/guix/commit/etc/guix-daemon.conf.in?id=d11b96eb5493231a5a35045505ff8ae8aa746b8e'>etc: Add explicit ‘--substitute-urls’ in guix-daemon service files.</a><span class='msg-avail'>...<span class='msg-tooltip'>Having substitute URLs explicitly listed in the service startup file
makes it clearer what should be modified to permanently change the list
of substitute URLs.

* config-daemon.ac: Rename ‘guix_substitute_urls’ to
‘GUIX_SUBSTITUTE_URLS’ and substitute it.
* nix/local.mk (etc/guix-%.service, etc/init.d/guix-daemon)
(etc/guix-%.conf): Substitute it.
* etc/guix-daemon.conf.in, etc/guix-daemon.service.in,
etc/init.d/guix-daemon.in: Add an explicit ‘--substitute-urls’ option.

Change-Id: Ie491b7fab5c42e54dca582801c03805a85de2bf9
</span></span></td><td>Ludovic Courtès</td></tr>