math/minizinc: Add patch to skip path that doesn't exist on FreeBSD

Also improve Makefile format.

math/minizinc/Makefile

@@ -1,5 +1,6 @@
 PORTNAME=	minizinc
 DISTVERSION=	2.5.5
+PORTREVISION=	1
 CATEGORIES=	math lang
 
 MAINTAINER=	yuri@FreeBSD.org
@@ -8,21 +9,24 @@ COMMENT=	Constraint modeling language
 LICENSE=	MPL20
 LICENSE_FILE=	${WRKSRC}/LICENSE.txt
 
+CONFLICTS_BUILD=	CoinMP
+
 LIB_DEPENDS=	libCbc.so:math/cbc \
 		libCgl.so:math/cgl \
 		libgecodekernel.so:devel/gecode \
 		libOsiClp.so:math/clp
 
 USES=		bison cmake compiler:c++11-lang
+USE_LDCONFIG=	yes
+
 USE_GITHUB=	yes
 GH_ACCOUNT=	MiniZinc
 GH_PROJECT=	libminizinc
-USE_LDCONFIG=	yes
-
-CXXFLAGS+=	-DFREEBSD_MZN_STDLIB_DIR="\\\"${DATADIR}\\\""
 
 CMAKE_ON=	BUILD_SHARED_LIBS
 
+CXXFLAGS+=	-DFREEBSD_MZN_STDLIB_DIR="\\\"${DATADIR}\\\""
+
 OPTIONS_DEFINE=		WITH_SCIP
 
 WITH_SCIP_DESC=		Build with the SCIP optimizer

math/minizinc/files/patch-lib_solver__config.cpp

@@ -0,0 +1,16 @@
+- Remove a non-existent directory from search.
+
+--- lib/solver_config.cpp.orig	2021-05-02 20:37:56 UTC
++++ lib/solver_config.cpp
+@@ -662,9 +662,11 @@ SolverConfigs::SolverConfigs(std::ostream& log) {
+       FileUtils::directory_exists("/usr/local/share")) {
+     _solverPath.emplace_back("/usr/local/share/minizinc/solvers");
+   }
++#  if !defined(__FreeBSD__)
+   if (_mznlibDir != "/usr/share/minizinc" && FileUtils::directory_exists("/usr/share")) {
+     _solverPath.emplace_back("/usr/share/minizinc/solvers");
+   }
++#  endif
+ #endif
+ }
+