Add new Makefile test case for upgraded syntax rules (#101719)

extensions/make/test/colorize-fixtures/makefile

@@ -84,3 +84,5 @@ var-$(nested-var)=val
 # but not so much.
 var-$(shell printf 2) := val2
 $(info Should be 'val2' here: $(var-2))
+
+export a ?= b:c

extensions/make/test/colorize-results/makefile.json

@@ -3353,5 +3353,71 @@
 			"light_vs": "string: #A31515",
 			"hc_black": "string: #CE9178"
 		}
+	},
+	{
+		"c": "export",
+		"t": "source.makefile keyword.control.export.makefile",
+		"r": {
+			"dark_plus": "keyword.control: #C586C0",
+			"light_plus": "keyword.control: #AF00DB",
+			"dark_vs": "keyword.control: #569CD6",
+			"light_vs": "keyword.control: #0000FF",
+			"hc_black": "keyword.control: #C586C0"
+		}
+	},
+	{
+		"c": " ",
+		"t": "source.makefile",
+		"r": {
+			"dark_plus": "default: #D4D4D4",
+			"light_plus": "default: #000000",
+			"dark_vs": "default: #D4D4D4",
+			"light_vs": "default: #000000",
+			"hc_black": "default: #FFFFFF"
+		}
+	},
+	{
+		"c": "a",
+		"t": "source.makefile variable.other.makefile",
+		"r": {
+			"dark_plus": "variable: #9CDCFE",
+			"light_plus": "variable: #001080",
+			"dark_vs": "default: #D4D4D4",
+			"light_vs": "default: #000000",
+			"hc_black": "variable: #9CDCFE"
+		}
+	},
+	{
+		"c": " ",
+		"t": "source.makefile",
+		"r": {
+			"dark_plus": "default: #D4D4D4",
+			"light_plus": "default: #000000",
+			"dark_vs": "default: #D4D4D4",
+			"light_vs": "default: #000000",
+			"hc_black": "default: #FFFFFF"
+		}
+	},
+	{
+		"c": "?=",
+		"t": "source.makefile punctuation.separator.key-value.makefile",
+		"r": {
+			"dark_plus": "default: #D4D4D4",
+			"light_plus": "default: #000000",
+			"dark_vs": "default: #D4D4D4",
+			"light_vs": "default: #000000",
+			"hc_black": "default: #FFFFFF"
+		}
+	},
+	{
+		"c": " b:c",
+		"t": "source.makefile",
+		"r": {
+			"dark_plus": "default: #D4D4D4",
+			"light_plus": "default: #000000",
+			"dark_vs": "default: #D4D4D4",
+			"light_vs": "default: #000000",
+			"hc_black": "default: #FFFFFF"
+		}
 	}
 ]
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