feat: Add osBuild as a reported device value (#298)

This adds `osBuild` as a new value that's being reported for every
device. This can be useful to tell apart release versions from beta
versions of the OS.

The technical name used by `sysctl` is "os version", but since the
`osVersion` key was already in use for reporting the marketing version
(e.g. 11.4), I used `osBuild` as the key instead.

Source/BugsnagKSCrashSysInfoParser.m

@@ -119,6 +119,7 @@
     BSGDictSetSafeObject(deviceState, report[@"machine"], @"model");
     BSGDictSetSafeObject(deviceState, report[@"system_name"], @"osName");
     BSGDictSetSafeObject(deviceState, report[@"system_version"], @"osVersion");
+    BSGDictSetSafeObject(deviceState, report[@"os_version"], @"osBuild");
     BSGDictSetSafeObject(deviceState, @(PLATFORM_WORD_SIZE), @"wordSize");
     BSGDictSetSafeObject(deviceState, @"Apple", @"manufacturer");
     BSGDictSetSafeObject(deviceState, report[@"jailbroken"], @"jailbroken");

Tests/BugsnagSessionTrackingPayloadTest.m

@@ -41,7 +41,7 @@ - (void)testPayloadSerialisation {
 - (void)testDeviceSerialisation {
     NSDictionary *device = self.payload[@"device"];
     XCTAssertNotNil(device);
-    XCTAssertEqual(7, device.count);
+    XCTAssertEqual(8, device.count);
 
     XCTAssertEqualObjects(device[@"manufacturer"], @"Apple");
     XCTAssertNotNil(device[@"model"]);

Tests/BugsnagSinkTests.m

@@ -259,9 +259,9 @@ - (void)testEventDevice {
     NSDictionary *device = event[@"device"];
     XCTAssertNotNil(device);
 #if TARGET_OS_IPHONE || TARGET_OS_TV || TARGET_IPHONE_SIMULATOR
-    XCTAssertEqual(17, device.count);
+    XCTAssertEqual(18, device.count);
 #else
-    XCTAssertEqual(16, device.count);
+    XCTAssertEqual(17, device.count);
 #endif
 
     XCTAssertEqualObjects(device[@"id"], @"f6d519a74213a57f8d052c53febfeee6f856d062");
@@ -270,6 +270,7 @@ - (void)testEventDevice {
     XCTAssertEqualObjects(device[@"modelNumber"], @"MacBookPro11,3");
     XCTAssertEqualObjects(device[@"osName"], @"iPhone OS");
     XCTAssertEqualObjects(device[@"osVersion"], @"8.1");
+    XCTAssertEqualObjects(device[@"osBuild"], @"14B25");
     XCTAssertEqualObjects(device[@"totalMemory"], @15065522176);
     XCTAssertNotNil(device[@"freeDisk"]);
     XCTAssertEqualObjects(device[@"timezone"], @"PST");