kbuild: do not quote string values in include/config/auto.conf

The previous commit fixed up all shell scripts to not include
include/config/auto.conf.

Now that include/config/auto.conf is only included by Makefiles,
we can change it into a more Make-friendly form.

Previously, Kconfig output string values enclosed with double-quotes
(both in the .config and include/config/auto.conf):

    CONFIG_X="foo bar"

Unlike shell, Make handles double-quotes (and single-quotes as well)
verbatim. We must rip them off when used.

There are some patterns:

  [1] $(patsubst "%",%,$(CONFIG_X))
  [2] $(CONFIG_X:"%"=%)
  [3] $(subst ",,$(CONFIG_X))
  [4] $(shell echo $(CONFIG_X))

These are not only ugly, but also fragile.

[1] and [2] do not work if the value contains spaces, like
   CONFIG_X=" foo bar "

[3] does not work correctly if the value contains double-quotes like
   CONFIG_X="foo\"bar"

[4] seems to work better, but has a cost of forking a process.

Anyway, quoted strings were always PITA for our Makefiles.

This commit changes Kconfig to stop quoting in include/config/auto.conf.

These are the string type symbols referenced in Makefiles or scripts:

    ACPI_CUSTOM_DSDT_FILE
    ARC_BUILTIN_DTB_NAME
    ARC_TUNE_MCPU
    BUILTIN_DTB_SOURCE
    CC_IMPLICIT_FALLTHROUGH
    CC_VERSION_TEXT
    CFG80211_EXTRA_REGDB_KEYDIR
    EXTRA_FIRMWARE
    EXTRA_FIRMWARE_DIR
    EXTRA_TARGETS
    H8300_BUILTIN_DTB
    INITRAMFS_SOURCE
    LOCALVERSION
    MODULE_SIG_HASH
    MODULE_SIG_KEY
    NDS32_BUILTIN_DTB
    NIOS2_DTB_SOURCE
    OPENRISC_BUILTIN_DTB
    SOC_CANAAN_K210_DTB_SOURCE
    SYSTEM_BLACKLIST_HASH_LIST
    SYSTEM_REVOCATION_KEYS
    SYSTEM_TRUSTED_KEYS
    TARGET_CPU
    UNUSED_KSYMS_WHITELIST
    XILINX_MICROBLAZE0_FAMILY
    XILINX_MICROBLAZE0_HW_VER
    XTENSA_VARIANT_NAME

I checked them one by one, and fixed up the code where necessary.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

certs/Makefile

@@ -6,7 +6,7 @@
 obj-$(CONFIG_SYSTEM_TRUSTED_KEYRING) += system_keyring.o system_certificates.o common.o
 obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist.o common.o
 obj-$(CONFIG_SYSTEM_REVOCATION_LIST) += revocation_certificates.o
-ifneq ($(CONFIG_SYSTEM_BLACKLIST_HASH_LIST),"")
+ifneq ($(CONFIG_SYSTEM_BLACKLIST_HASH_LIST),)
 obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist_hashes.o
 else
 obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist_nohashes.o
@@ -17,8 +17,6 @@ quiet_cmd_extract_certs  = CERT    $@
 
 $(obj)/system_certificates.o: $(obj)/x509_certificate_list
 
-CONFIG_SYSTEM_TRUSTED_KEYS := $(CONFIG_SYSTEM_TRUSTED_KEYS:"%"=%)
-
 $(obj)/x509_certificate_list: $(CONFIG_SYSTEM_TRUSTED_KEYS) scripts/extract-cert FORCE
 	$(call if_changed,extract_certs,$(if $(CONFIG_SYSTEM_TRUSTED_KEYS),$<,""))
 
@@ -46,7 +44,7 @@ ifdef SIGN_KEY
 # We do it this way rather than having a boolean option for enabling an
 # external private key, because 'make randconfig' might enable such a
 # boolean option and we unfortunately can't make it depend on !RANDCONFIG.
-ifeq ($(CONFIG_MODULE_SIG_KEY),"certs/signing_key.pem")
+ifeq ($(CONFIG_MODULE_SIG_KEY),certs/signing_key.pem)
 
 keytype-$(CONFIG_MODULE_SIG_KEY_TYPE_ECDSA) := -newkey ec -pkeyopt ec_paramgen_curve:secp384r1
 
@@ -69,8 +67,6 @@ $(obj)/x509.genkey:
 
 endif # CONFIG_MODULE_SIG_KEY
 
-CONFIG_MODULE_SIG_KEY := $(CONFIG_MODULE_SIG_KEY:"%"=%)
-
 # If CONFIG_MODULE_SIG_KEY isn't a PKCS#11 URI, depend on it
 ifneq ($(filter-out pkcs11:%, %(CONFIG_MODULE_SIG_KEY)),)
 X509_DEP := $(CONFIG_MODULE_SIG_KEY)
@@ -86,8 +82,6 @@ targets += signing_key.x509
 
 $(obj)/revocation_certificates.o: $(obj)/x509_revocation_list
 
-CONFIG_SYSTEM_REVOCATION_KEYS := $(CONFIG_SYSTEM_REVOCATION_KEYS:"%"=%)
-
 $(obj)/x509_revocation_list: $(CONFIG_SYSTEM_REVOCATION_KEYS) scripts/extract-cert FORCE
 	$(call if_changed,extract_certs,$(if $(CONFIG_SYSTEM_REVOCATION_KEYS),$<,""))