Update core version during build (#1379)

* Update core version during build

During build we need to also update the core version file, otherwise, the internal metrics show "latest" instead of the real version.

* Update Makefile

Makefile

@@ -38,9 +38,11 @@ MISSPELL=misspell -error
 MISSPELL_CORRECTION=misspell -w
 
 BUILD_INFO_IMPORT_PATH=github.com/signalfx/splunk-otel-collector/internal/version
+BUILD_INFO_IMPORT_PATH_CORE=go.opentelemetry.io/collector/internal/version
 VERSION=$(shell git describe --match "v[0-9]*" HEAD)
 BUILD_X1=-X $(BUILD_INFO_IMPORT_PATH).Version=$(VERSION)
-BUILD_INFO=-ldflags "${BUILD_X1}"
+BUILD_X2=-X $(BUILD_INFO_IMPORT_PATH_CORE).Version=$(VERSION)
+BUILD_INFO=-ldflags "${BUILD_X1} ${BUILD_X2}"
 
 SMART_AGENT_RELEASE=$(shell cat internal/buildscripts/packaging/smart-agent-release.txt)
 SKIP_COMPILE=false