Travis: optimize macOS deploy build

- Turns on the -DENABLE_LTO flag during deploy
- Turns off the -DENABLE_OPENMP flag during test

.travis/build-macos.sh

@@ -1,14 +1,9 @@
 #!/bin/sh -xe
 
-if echo $TRAVIS_TAG | grep ^v; then
-    BUILD_TYPE=RelWithDebInfo
-else
-    BUILD_TYPE=Debug
-fi
-
 mkdir build || true
 cd build
 
+OSX_TARGET="10.9"
 LLVM_PREFIX=$(brew --prefix llvm@9)
 export CC="${LLVM_PREFIX}/bin/clang"
 export CXX="${CC}++"
@@ -16,10 +11,19 @@ export LDFLAGS="-L${LLVM_PREFIX}/lib -Wl,-rpath,${LLVM_PREFIX}/lib" \
 export CFLAGS="-I${LLVM_PREFIX}/include"
 export CPPFLAGS="-I${LLVM_PREFIX}/include"
 
-cmake \
-    -DCMAKE_OSX_DEPLOYMENT_TARGET=10.9 \
-    -DCMAKE_BUILD_TYPE=$BUILD_TYPE .. \
-    -DENABLE_OPENMP=ON
+if echo $TRAVIS_TAG | grep ^v; then
+    BUILD_TYPE=RelWithDebInfo
+    cmake \
+        -DCMAKE_OSX_DEPLOYMENT_TARGET="${OSX_TARGET}" \
+        -DCMAKE_BUILD_TYPE="${BUILD_TYPE}" .. \
+        -DENABLE_OPENMP=ON \
+        -DENABLE_LTO=ON
+else
+    BUILD_TYPE=Debug
+        cmake \
+        -DCMAKE_OSX_DEPLOYMENT_TARGET="${OSX_TARGET}" \
+        -DCMAKE_BUILD_TYPE="${BUILD_TYPE}" ..
+fi
 
-cmake --build . --config $BUILD_TYPE -- -j$(nproc)
+cmake --build . --config "${BUILD_TYPE}" -- -j$(nproc)
 make -j$(nproc) test_solvespace