package/luarocks: rework configuration file for per-package directories

Currently, luarocks.mk generates a configuration file with hardcoded
STAGING_DIR, TARGET_DIR, TARGET_CC, LUAROCKS_CFLAGS and TARGET_LDFLAGS
values. This is not compatible with per-package directories, where the
value of STAGING_DIR, TARGET_DIR, TARGET_CC and possibly
TARGET_CFLAGS/TARGET_LDFLAGS may be different from one package to the
other.

Based on input from François Perrad, this commit:

 - Changes the Luarocks configuration file to use os_getenv() for the
   appropriate variables. Since the contents of this file is not
   fixed, it is no longer generated by luarocks.mk using a series of
   'echo' but simply concatenated with the rest of the Luarocks
   configuration file.

 - Adjusts LUAROCKS_RUNV_ENV so that the necessary environment
   variables are now passed.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Acked-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/luarocks/luarocks-br-config.lua

@@ -0,0 +1,13 @@
+-- BR cross-compilation
+local function getenv (name) return os_getenv(name) or '' end
+variables.LUA_INCDIR = getenv('STAGING_DIR') .. [[/usr/include]]
+variables.LUA_LIBDIR = getenv('STAGING_DIR') .. [[/usr/lib]]
+variables.CC = getenv('TARGET_CC')
+variables.LD = getenv('TARGET_CC')
+variables.CFLAGS = getenv('TARGET_CFLAGS')
+variables.LIBFLAG = [[-shared ]] .. getenv('TARGET_LDFLAGS')
+external_deps_dirs = { getenv('STAGING_DIR') .. [[/usr]] }
+gcc_rpath = false
+rocks_trees = { getenv('TARGET_DIR') .. [[/usr]] }
+wrap_bin_scripts = false
+deps_mode = [[none]]

package/luarocks/luarocks.mk

@@ -30,23 +30,16 @@ endef
 define HOST_LUAROCKS_INSTALL_CMDS
 	rm -f $(LUAROCKS_CONFIG_FILE)
 	$(MAKE1) -C $(@D) install
-	echo "-- BR cross-compilation"                                  >> $(LUAROCKS_CONFIG_FILE)
-	echo "variables.LUA_INCDIR = [[$(STAGING_DIR)/usr/include]]"    >> $(LUAROCKS_CONFIG_FILE)
-	echo "variables.LUA_LIBDIR = [[$(STAGING_DIR)/usr/lib]]"        >> $(LUAROCKS_CONFIG_FILE)
-	echo "variables.CC = [[$(TARGET_CC)]]"                          >> $(LUAROCKS_CONFIG_FILE)
-	echo "variables.LD = [[$(TARGET_CC)]]"                          >> $(LUAROCKS_CONFIG_FILE)
-	echo "variables.CFLAGS = [[$(LUAROCKS_CFLAGS)]]"                >> $(LUAROCKS_CONFIG_FILE)
-	echo "variables.LIBFLAG = [[-shared $(TARGET_LDFLAGS)]]"        >> $(LUAROCKS_CONFIG_FILE)
-	echo "external_deps_dirs = { [[$(STAGING_DIR)/usr]] }"          >> $(LUAROCKS_CONFIG_FILE)
-	echo "gcc_rpath = false"                                        >> $(LUAROCKS_CONFIG_FILE)
-	echo "rocks_trees = { [[$(TARGET_DIR)/usr]] }"                  >> $(LUAROCKS_CONFIG_FILE)
-	echo "wrap_bin_scripts = false"                                 >> $(LUAROCKS_CONFIG_FILE)
-	echo "deps_mode = [[none]]"                                     >> $(LUAROCKS_CONFIG_FILE)
+	cat $(HOST_LUAROCKS_PKGDIR)/luarocks-br-config.lua >> $(LUAROCKS_CONFIG_FILE)
 endef
 
 $(eval $(host-generic-package))
 
-LUAROCKS_RUN_ENV = LUA_PATH="$(HOST_DIR)/share/lua/$(LUAINTERPRETER_ABIVER)/?.lua"
+LUAROCKS_RUN_ENV = \
+	LUA_PATH="$(HOST_DIR)/share/lua/$(LUAINTERPRETER_ABIVER)/?.lua" \
+	TARGET_CC="$(TARGET_CC)" \
+	TARGET_CFLAGS="$(LUAROCKS_CFLAGS)" \
+	TARGET_LDFLAGS="$(TARGET_LDFLAGS)"
 LUAROCKS_RUN_CMD = $(LUA_RUN) $(HOST_DIR)/bin/luarocks
 
 define LUAROCKS_FINALIZE_TARGET