update macos deployment target to 10.15 (#19)

* update macos deployment target to 12.0

* downgrade to 10.15

Author: michaelknoch

JNI.xcodeproj/project.pbxproj

@@ -265,7 +265,7 @@
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
 				ENABLE_NS_ASSERTIONS = YES;
 				GCC_OPTIMIZATION_LEVEL = 0;
-				MACOSX_DEPLOYMENT_TARGET = 10.10;
+				MACOSX_DEPLOYMENT_TARGET = 10.15;
 				ONLY_ACTIVE_ARCH = YES;
 				OTHER_SWIFT_FLAGS = "-DXcode";
 				PRODUCT_NAME = "$(TARGET_NAME)";
@@ -335,7 +335,7 @@
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
 				GCC_OPTIMIZATION_LEVEL = s;
-				MACOSX_DEPLOYMENT_TARGET = 10.10;
+				MACOSX_DEPLOYMENT_TARGET = 10.15;
 				OTHER_SWIFT_FLAGS = "-DXcode";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = macosx;