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

Makefile

@@ -12,7 +12,7 @@ NC     := \033[0m
 GOFLAGS=
 LDFLAGS=
 GOCMD=go
-GOBUILD=$(GOCMD) build $(GOFLAGS) $(if $(LDFLAGS),-ldflags='$(LDFLAGS)')
+GOBUILD=$(GOCMD) build $(GOFLAGS) $(if $(LDFLAGS),-ldflags="$(LDFLAGS)")
 GOGENERATE=$(GOCMD) generate
 GOCLEAN=$(GOCMD) clean
 GOTEST=$(GOCMD) test
@@ -51,7 +51,7 @@ $(OBITOOLS_PREFIX)$(notdir $(1)): $(BUILD_DIR) $(1) pkg/obioptions/version.go
 	@echo -n - Building obitool $(notdir $(1))...
 	@$(GOBUILD)  -o $(BUILD_DIR)/$(OBITOOLS_PREFIX)$(notdir $(1)) ./$(1) \
 	             2> $(OBITOOLS_PREFIX)$(notdir $(1)).log \
-				 || cat $(OBITOOLS_PREFIX)$(notdir $(1)).log
+				 || { cat $(OBITOOLS_PREFIX)$(notdir $(1)).log; rm -f $(OBITOOLS_PREFIX)$(notdir $(1)).log; exit 1; }
 	@rm -f $(OBITOOLS_PREFIX)$(notdir $(1)).log
 	@echo Done.
 endef

go.mod

@@ -1,6 +1,6 @@
 module git.metabarcoding.org/obitools/obitools4/obitools4
 
-go 1.25.0
+go 1.26.1
 
 require (
 	github.com/DavidGamba/go-getoptions v0.33.0

go.work

@@ -1,3 +1,3 @@
-go 1.25.0
+go 1.26.1
 
 use .

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