game_launch: force link libm on Linux to workaround HL25 bug

HL25 doesn't link libm probably because of toolchain updates, where
--Wl,--as-needed became the default.

hl_linux is linked to libm which is why they probably didn't noticed this bug.

Workaround until Valve fixes it: https://github.com/ValveSoftware/halflife/issues/3492

game_launch/wscript

@@ -21,21 +21,19 @@ def configure(conf):
 	conf.define_cond('XASH_DISABLE_MENU_CHANGEGAME', conf.options.DISABLE_MENU_CHANGEGAME)
 
 def build(bld):
-	libs = ['sdk_includes']
 	source = ['game.cpp']
-	defines = []
 
-	if bld.env.DEST_OS != 'win32':
-		libs += [ 'DL' ]
-	else:
-		libs += ['USER32', 'SHELL32']
+	if bld.env.DEST_OS == 'win32':
 		source += ['game.rc']
 
+	# Half-Life 25th anniversary update doesn't have server library explicitly linked to libm
+	if bld.env.DEST_OS == 'linux':
+		bld.env.LDFLAGS += ['-Wl,--no-as-needed', '-lm']
+
 	bld(source = source,
 		target   = 'xash3d', # hl.exe
 		features = 'c cxx cxxprogram',
-		use      = libs,
-		defines  = defines,
+		use      = 'sdk_includes DL USER32 SHELL32',
 		rpath    = bld.env.DEFAULT_RPATH,
 		install_path = bld.env.BINDIR,
 		subsystem = bld.env.MSVC_SUBSYSTEM