make: improve check for externally managed Python

Move PYTHON_EXTERNALLY_MANAGED and PIP_BREAK_SYSTEM_PACKAGES
into Makefile.install to avoid code duplication. In addition, add
PIPFLAGS variable to enable specifying pip options during installation.
This is particularly useful for packaging, where it is common for `pip install`
to run in an environment with pre-installed dependencies and without internet
access. In such environment, we need to specify the following options:

    --no-build-isolation --no-index --no-deps

Signed-off-by: Radostin Stoyanov <rstoyanov@fedoraproject.org>

Makefile.install

@@ -29,6 +29,26 @@ LIBDIR ?= $(PREFIX)/lib
 export PREFIX BINDIR SBINDIR MANDIR RUNDIR
 export LIBDIR INCLUDEDIR LIBEXECDIR PLUGINDIR
 
+# Detect externally managed Python environment (PEP 668).
+PYTHON_EXTERNALLY_MANAGED := $(shell $(PYTHON) -c 'import os, sysconfig; print(int(os.path.isfile(os.path.join(sysconfig.get_path("stdlib"), "EXTERNALLY-MANAGED"))))')
+PIP_BREAK_SYSTEM_PACKAGES ?= 0
+
+# If Python environment is externally managed and PIP_BREAK_SYSTEM_PACKAGES is not set, skip pip install.
+SKIP_PIP_INSTALL := 0
+ifeq ($(PYTHON_EXTERNALLY_MANAGED),1)
+ifeq ($(PIP_BREAK_SYSTEM_PACKAGES),0)
+	SKIP_PIP_INSTALL := 1
+endif
+endif
+
+# Default flags for pip install:
+# --upgrade: Upgrade crit/pycriu packages
+# --ignore-installed: Ignore existing packages and reinstall them
+# --progress-bar off: Suppress the progress bar for cleaner output
+PIPFLAGS ?= --upgrade --ignore-installed --progress-bar off
+
+export SKIP_PIP_INSTALL PIPFLAGS
+
 install-man:
 	$(Q) $(MAKE) -C Documentation install
 .PHONY: install-man

crit/Makefile

@@ -1,6 +1,3 @@
-PYTHON_EXTERNALLY_MANAGED := $(shell $(PYTHON) -c 'import os, sysconfig; print(int(os.path.isfile(os.path.join(sysconfig.get_path("stdlib"), "EXTERNALLY-MANAGED"))))')
-PIP_BREAK_SYSTEM_PACKAGES := 0
-
 VERSION_FILE := $(if $(obj),$(addprefix $(obj)/,crit/version.py),crit/version.py)
 
 all-y	+= ${VERSION_FILE}
@@ -10,31 +7,21 @@ ${VERSION_FILE}:
 	$(Q) echo "__version__ = '${CRIU_VERSION}'" > $@
 
 install: ${VERSION_FILE}
-ifeq ($(PYTHON_EXTERNALLY_MANAGED),1)
-ifeq ($(PIP_BREAK_SYSTEM_PACKAGES),0)
-	$(E) "  SKIP INSTALL crit: Externally managed python environment (See PEP 668 for more information)"
-	$(E) "  Consider using PIP_BREAK_SYSTEM_PACKAGES=1 make install"
-else
+ifeq ($(SKIP_PIP_INSTALL),0)
 	$(E) "  INSTALL " crit
-	$(Q) $(PYTHON) -m pip install --upgrade --ignore-installed --prefix=$(DESTDIR)$(PREFIX) ./crit
-endif
+	$(Q) $(PYTHON) -m pip install $(PIPFLAGS) --prefix=$(DESTDIR)$(PREFIX) ./crit
 else
-	$(E) "  INSTALL " crit
-	$(Q) $(PYTHON) -m pip install --upgrade --ignore-installed --prefix=$(DESTDIR)$(PREFIX) ./crit
+	$(E) " SKIP INSTALL crit: Externally managed Python environment"
+	$(E) " Consider using PIP_BREAK_SYSTEM_PACKAGES=1"
 endif
 .PHONY: install
 
 uninstall:
-ifeq ($(PYTHON_EXTERNALLY_MANAGED),1)
-ifeq ($(PIP_BREAK_SYSTEM_PACKAGES),0)
-	$(E) " SKIP UNINSTALL crit: Externally managed python environment (See PEP 668 for more information)"
-	$(E) " Consider using PIP_BREAK_SYSTEM_PACKAGES=1 make uninstall"
-else
+ifeq ($(SKIP_PIP_INSTALL),0)
 	$(E) " UNINSTALL" crit
 	$(Q) $(PYTHON) ./scripts/uninstall_module.py --prefix=$(DESTDIR)$(PREFIX) crit
-endif
 else
-	$(E) " UNINSTALL" crit
-	$(Q) $(PYTHON) ./scripts/uninstall_module.py --prefix=$(DESTDIR)$(PREFIX) crit
+	$(E) " SKIP UNINSTALL crit: Externally managed python environment"
+	$(E) " Consider using PIP_BREAK_SYSTEM_PACKAGES=1"
 endif
 .PHONY: uninstall

lib/Makefile

@@ -4,9 +4,6 @@ UAPI_HEADERS		:= lib/c/criu.h images/rpc.proto images/rpc.pb-c.h criu/include/ve
 
 all-y	+= lib-c lib-a lib-py
 
-PYTHON_EXTERNALLY_MANAGED := $(shell $(PYTHON) -c 'import os, sysconfig; print(int(os.path.isfile(os.path.join(sysconfig.get_path("stdlib"), "EXTERNALLY-MANAGED"))))')
-PIP_BREAK_SYSTEM_PACKAGES := 0
-
 #
 # C language bindings.
 lib/c/Makefile: ;
@@ -57,17 +54,12 @@ install: lib-c lib-a lib-py lib/c/criu.pc.in
 	$(Q) mkdir -p $(DESTDIR)$(LIBDIR)/pkgconfig
 	$(Q) sed -e 's,@version@,$(CRIU_VERSION),' -e 's,@libdir@,$(LIBDIR),' -e 's,@includedir@,$(dir $(INCLUDEDIR)/criu/),' lib/c/criu.pc.in > lib/c/criu.pc
 	$(Q) install -m 644 lib/c/criu.pc $(DESTDIR)$(LIBDIR)/pkgconfig
-ifeq ($(PYTHON_EXTERNALLY_MANAGED),1)
-ifeq ($(PIP_BREAK_SYSTEM_PACKAGES),0)
-	$(E) "  SKIP INSTALL pycriu: Externally managed python environment (See PEP 668 for more information)"
-	$(E) "  Consider using PIP_BREAK_SYSTEM_PACKAGES=1 make install"
-else
+ifeq ($(SKIP_PIP_INSTALL),0)
 	$(E) "  INSTALL " pycriu
-	$(Q) $(PYTHON) -m pip install --upgrade --ignore-installed --prefix=$(DESTDIR)$(PREFIX) ./lib
-endif
+	$(Q) $(PYTHON) -m pip install $(PIPFLAGS) --prefix=$(DESTDIR)$(PREFIX) ./lib
 else
-	$(E) "  INSTALL " pycriu
-	$(Q) $(PYTHON) -m pip install --upgrade --ignore-installed --prefix=$(DESTDIR)$(PREFIX) ./lib
+	$(E) " SKIP INSTALL pycriu: Externally managed Python environment"
+	$(E) " Consider using PIP_BREAK_SYSTEM_PACKAGES=1"
 endif
 .PHONY: install
 
@@ -80,16 +72,11 @@ uninstall:
 	$(Q) $(RM) $(addprefix $(DESTDIR)$(INCLUDEDIR)/criu/,$(notdir $(UAPI_HEADERS)))
 	$(E) " UNINSTALL" pkgconfig/criu.pc
 	$(Q) $(RM) $(addprefix $(DESTDIR)$(LIBDIR)/pkgconfig/,criu.pc)
-ifeq ($(PYTHON_EXTERNALLY_MANAGED),1)
-ifeq ($(PIP_BREAK_SYSTEM_PACKAGES),0)
-	$(E) " SKIP UNINSTALL pycriu: Externally managed python environment (See PEP 668 for more information)"
-	$(E) " Consider using PIP_BREAK_SYSTEM_PACKAGES=1 make uninstall"
-else
+ifeq ($(SKIP_PIP_INSTALL),0)
 	$(E) " UNINSTALL" pycriu
 	$(Q) $(PYTHON) ./scripts/uninstall_module.py --prefix=$(DESTDIR)$(PREFIX) pycriu
-endif
 else
-	$(E) " UNINSTALL" pycriu
-	$(Q) $(PYTHON) ./scripts/uninstall_module.py --prefix=$(DESTDIR)$(PREFIX) pycriu
+	$(E) " SKIP UNINSTALL pycriu: Externally managed Python environment"
+	$(E) " Consider using PIP_BREAK_SYSTEM_PACKAGES=1"
 endif
 .PHONY: uninstall