package/pkg-*.mk: do not conditionally set empty variables

Setting an unset variable to an empty value is useless in make; an unset
variable just expands to an empty string anyway. So what we do currently
has no side effect:

    variable set and not empty   -> variable not modified
    variable set and empty       -> variable not modified
    variable unset               -> set to an empty string

However, additional variables do have an impact on the parsing time of
the Makefiles, and the more variables, the more collisions in the hash
table used internally by make, which slows down the parsing.

By dropping those conditionally-set-empty variables, we gain about 3%:

    Run     Before  After
    1       5.572   5.325
    2       5.434   5.354
    3       5.490   5.320
    4       5.525   5.330
    5       5.476   5.330
    6       5.511   5.434
    7       5.498   5.388
    8       5.524   5.371
    9       5.479   5.346
    10      5.637   5.324
    Mean:   5.515   5.352

Yeah, 0.163s does not look like much, and this does not make
autocompletion any more usable. Still, that 3% gain is not to be
ashamed of either.

Note that there are 3 others case where we do set empty variables, but
those are unconditional and serve other purposes:

  - pkg-virtual: this is done on purpose to avoid a bug when the
    environment may have TOOLCHAIN_VERSION or _SOURCE set, and we really
    want those to be empty, so the assignment is not conditional;

  - pkg-python: the reason for setting those to empty is dubious at
    best; it's been there since the inception of the python infra, back
    in 2013; still, the case is different than this patch addresses;

  - pkg-toolchain-external: this is the case for a toolchain already
    installed, so indeed we want to set _SOURCE and _VERSION to empty.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/pkg-autotools.mk

@@ -160,10 +160,6 @@ ifeq ($(4),host)
  $(2)_AUTORECONF_OPTS ?= $$($(3)_AUTORECONF_OPTS)
 endif
 
-$(2)_CONF_ENV			?=
-$(2)_CONF_OPTS			?=
-$(2)_MAKE_ENV			?=
-$(2)_MAKE_OPTS			?=
 $(2)_INSTALL_OPTS                ?= install
 $(2)_INSTALL_STAGING_OPTS	?= DESTDIR=$$(STAGING_DIR) install
 $(2)_INSTALL_TARGET_OPTS		?= DESTDIR=$$(TARGET_DIR) install

package/pkg-cmake.mk

@@ -51,11 +51,7 @@ endif
 
 define inner-cmake-package
 
-$(2)_CONF_ENV			?=
-$(2)_CONF_OPTS			?=
 $(2)_MAKE			?= $$(MAKE)
-$(2)_MAKE_ENV			?=
-$(2)_MAKE_OPTS			?=
 $(2)_INSTALL_OPTS		?= install
 $(2)_INSTALL_STAGING_OPTS	?= DESTDIR=$$(STAGING_DIR) install/fast
 $(2)_INSTALL_TARGET_OPTS	?= DESTDIR=$$(TARGET_DIR) install/fast

package/pkg-generic.mk

@@ -540,8 +540,6 @@ $(2)_DIR	=  $$(BUILD_DIR)/$$($(2)_BASENAME)
 ifndef $(2)_SUBDIR
  ifdef $(3)_SUBDIR
   $(2)_SUBDIR = $$($(3)_SUBDIR)
- else
-  $(2)_SUBDIR ?=
  endif
 endif
 
@@ -838,31 +836,6 @@ $(2)_EXTRACT_CMDS ?= \
 		$$(TAR_OPTIONS) -)
 
 # pre/post-steps hooks
-$(2)_PRE_DOWNLOAD_HOOKS         ?=
-$(2)_POST_DOWNLOAD_HOOKS        ?=
-$(2)_PRE_EXTRACT_HOOKS          ?=
-$(2)_POST_EXTRACT_HOOKS         ?=
-$(2)_PRE_RSYNC_HOOKS            ?=
-$(2)_POST_RSYNC_HOOKS           ?=
-$(2)_PRE_PATCH_HOOKS            ?=
-$(2)_POST_PATCH_HOOKS           ?=
-$(2)_PRE_CONFIGURE_HOOKS        ?=
-$(2)_POST_CONFIGURE_HOOKS       ?=
-$(2)_PRE_BUILD_HOOKS            ?=
-$(2)_POST_BUILD_HOOKS           ?=
-$(2)_PRE_INSTALL_HOOKS          ?=
-$(2)_POST_INSTALL_HOOKS         ?=
-$(2)_PRE_INSTALL_STAGING_HOOKS  ?=
-$(2)_POST_INSTALL_STAGING_HOOKS ?=
-$(2)_PRE_INSTALL_TARGET_HOOKS   ?=
-$(2)_POST_INSTALL_TARGET_HOOKS  ?=
-$(2)_PRE_INSTALL_IMAGES_HOOKS   ?=
-$(2)_POST_INSTALL_IMAGES_HOOKS  ?=
-$(2)_PRE_LEGAL_INFO_HOOKS       ?=
-$(2)_POST_LEGAL_INFO_HOOKS      ?=
-$(2)_TARGET_FINALIZE_HOOKS      ?=
-$(2)_ROOTFS_PRE_CMD_HOOKS       ?=
-
 $(2)_POST_PREPARE_HOOKS += FIXUP_PYTHON_SYSCONFIGDATA
 
 ifeq ($$($(2)_TYPE),target)

package/pkg-kconfig.mk

@@ -81,9 +81,6 @@ define inner-kconfig-package
 # Default values
 $(2)_MAKE ?= $$(MAKE)
 $(2)_KCONFIG_EDITORS ?= menuconfig
-$(2)_KCONFIG_OPTS ?=
-$(2)_KCONFIG_FIXUP_CMDS ?=
-$(2)_KCONFIG_FRAGMENT_FILES ?=
 $(2)_KCONFIG_DOTCONFIG ?= .config
 $(2)_KCONFIG_SUPPORTS_DEFCONFIG ?= YES
 

package/pkg-meson.mk

@@ -45,10 +45,6 @@ NINJA_OPTS	= $(if $(VERBOSE),-v) -j$(PARALLEL_JOBS)
 
 define inner-meson-package
 
-$(2)_CONF_ENV		?=
-$(2)_CONF_OPTS		?=
-$(2)_NINJA_ENV		?=
-
 #
 # Configure step. Only define it if not already defined by the package
 # .mk file. And take care of the differences between host and target

package/pkg-python.mk

@@ -108,10 +108,6 @@ HOST_PKG_PYTHON_SETUPTOOLS_INSTALL_OPTS = \
 
 define inner-python-package
 
-$(2)_ENV         ?=
-$(2)_BUILD_OPTS   ?=
-$(2)_INSTALL_OPTS ?=
-
 ifndef $(2)_SETUP_TYPE
  ifdef $(3)_SETUP_TYPE
   $(2)_SETUP_TYPE = $$($(3)_SETUP_TYPE)

package/pkg-qmake.mk

@@ -40,10 +40,6 @@ endef
 
 define inner-qmake-package
 
-$(2)_CONF_ENV			?=
-$(2)_CONF_OPTS			?=
-$(2)_MAKE_ENV			?=
-$(2)_MAKE_OPTS			?=
 $(2)_INSTALL_STAGING_OPTS	?= install
 $(2)_INSTALL_TARGET_OPTS	?= $$($(2)_INSTALL_STAGING_OPTS)
 

package/pkg-waf.mk

@@ -49,11 +49,6 @@ else
 $(2)_WAF ?= ./waf
 endif
 
-$(2)_BUILD_OPTS				?=
-$(2)_INSTALL_STAGING_OPTS		?=
-$(2)_INSTALL_TARGET_OPTS		?=
-$(2)_WAF_OPTS				?=
-
 #
 # Configure step. Only define it if not already defined by the package
 # .mk file.