cargo_build_script: Add regression for revert #2925

Existing test passes with #2911 and #2922.
However even #2922 was breaking something.
I suspect case like this is the cause.

test/cargo_build_script/cc_args_and_env/BUILD.bazel

@@ -3,13 +3,16 @@ load(
     "isystem_absolute_test",
     "isystem_relative_test",
     "sysroot_absolute_test",
+    "sysroot_absolute2_test",
     "sysroot_relative_test",
 )
 
 sysroot_relative_test(name = "sysroot_relative_test")
 
 sysroot_absolute_test(name = "sysroot_absolute_test")
 
+sysroot_absolute2_test(name = "sysroot_absolute2_test")
+
 isystem_relative_test(name = "isystem_relative_test")
 
 isystem_absolute_test(name = "isystem_absolute_test")

test/cargo_build_script/cc_args_and_env/cc_args_and_env_test.bzl

@@ -173,6 +173,17 @@ def sysroot_absolute_test(name):
         expected_cflags = ["--sysroot=/test/absolute/sysroot"],
     )
 
+def sysroot_absolute2_test(name):
+    cargo_build_script_with_extra_cc_compile_flags(
+        name = "%s/cargo_build_script" % name,
+        extra_cc_compile_flags = ["--sysroot=/test/absolute/sysroot", "test/relative/another"],
+    )
+    cc_args_and_env_analysis_test(
+        name = name,
+        target_under_test = "%s/cargo_build_script" % name,
+        expected_cflags = ["--sysroot=/test/absolute/sysroot", "test/relative/another"],
+    )
+
 def isystem_relative_test(name):
     cargo_build_script_with_extra_cc_compile_flags(
         name = "%s/cargo_build_script" % name,