math_opt: build fixup

ortools/math_opt/BUILD.bazel

@@ -90,6 +90,7 @@ proto_library(
         "//ortools/gscip:gscip_proto",
         "//ortools/math_opt/solvers:glpk_proto",
         "//ortools/math_opt/solvers:gurobi_proto",
+        "//ortools/math_opt/solvers:highs_proto",
         "//ortools/sat:sat_parameters_proto",
         "@com_google_protobuf//:duration_proto",
     ],

ortools/math_opt/cpp/BUILD.bazel

@@ -291,6 +291,7 @@ cc_library(
         "@com_google_absl//absl/base:core_headers",
         "@com_google_absl//absl/strings",
         "@com_google_absl//absl/synchronization",
+        "@com_google_protobuf//:protobuf",
     ],
 )
 

ortools/math_opt/solvers/BUILD.bazel

@@ -341,3 +341,13 @@ proto_library(
     name = "glpk_proto",
     srcs = ["glpk.proto"],
 )
+
+cc_proto_library(
+    name = "highs_cc_proto",
+    deps = [":highs_proto"],
+)
+
+proto_library(
+    name = "highs_proto",
+    srcs = ["highs.proto"],
+)