Build improvements and Go version update

- Update Go version from 1.25.0 to 1.26.1 in go.mod and go.work
- Fix Makefile: quote LDFLAGS to handle spaces safely in -ldflags
- Improve build error handling: on failure, cat log then cleanup and exit with error code
- Update install_obitools.sh: properly set GOROOT, GOPATH, and GOTOOLCHAIN; ensure GOPATH directory is created

install_obitools.sh

@@ -185,14 +185,16 @@ echo "Installing Go from: $GOURL" 1>&2
 
 curl --progress-bar "$GOURL" | tar zxf -
 
-PATH="$(pwd)/go/bin:$PATH"
+export GOROOT="$(pwd)/go"
+PATH="${GOROOT}/bin:$PATH"
 export PATH
-GOPATH="$(pwd)/go"
-export GOPATH
+export GOPATH="$(pwd)/gopath"
 export GOCACHE="$(pwd)/cache"
+export GOTOOLCHAIN=local
 
+echo "GOROOT=$GOROOT" 1>&2
 echo "GOCACHE=$GOCACHE" 1>&2
-mkdir -p "$GOCACHE"
+mkdir -p "$GOPATH" "$GOCACHE"
 
 # Download OBITools4 source
 echo "Downloading OBITools4 v${VERSION}..." 1>&2