BUILD: makefile: move the compiler option detection stuff to compiler.mk

There's quite a large barely readable functions block in the makefile
dedicated to compiler option support. It provides no value here and
makes it harder to find user-configurable stuff, so let's move it to
include/make/compiler.mk to keep the makefile a bit cleaner. It's better
to keep the options themselves in the makefile however.

Makefile

@@ -124,49 +124,7 @@
 #   DEBUG_USE_ABORT: use abort() for program termination, see include/haproxy/bug.h for details
 
 include include/make/verbose.mk
-
+include include/make/compiler.mk
-# WARNING: Do not change cc-opt, cc-opt-alt or cc-warning without checking if
-#          clang bug #49364 is fixed. stderr is redirected to /dev/null on
-#          purpose, to work around a clang 11 bug that crashes if stderr is
-#          redirected to stdin.
-#
-# Function used to detect support of a given option by the compiler.
-# Usage: CFLAGS += $(call cc-opt,option). Eg: $(call cc-opt,-fwrapv)
-# Note: ensure the referencing variable is assigned using ":=" and not "=" to
-#       call it only once.
-cc-opt = $(shell set -e; if $(CC) -Werror $(1) -E -xc - -o /dev/null </dev/null >&0 2>/dev/null; then echo "$(1)"; fi;)
-
-# same but tries with $2 if $1 is not supported
-cc-opt-alt = $(if $(shell set -e; if $(CC) -Werror $(1) -E -xc - -o /dev/null </dev/null >&0 2>/dev/null; then echo 1;fi),$(1),$(call cc-opt,$(2)))
-
-# validate a list of options one at a time
-cc-all-opts  = $(foreach a,$(1),$(call cc-opt,$(a)))
-
-# try to pass plenty of options at once, take them on success or try them
-# one at a time on failure and keep successful ones. This is handy to quickly
-# validate most common options.
-cc-all-fast = $(if $(call cc-opt,$(1)),$(1),$(call cc-all-opts,$(1)))
-
-# Below we verify that the compiler supports any -Wno-something option to
-# disable any warning, or if a special option is needed to achieve that. This
-# will allow to get rid of testing when the compiler doesn't care. The result
-# is made of two variables:
-#  - cc-anywno that's non-empty if the compiler supports disabling anything
-#  - cc-wnouwo that may contain an option needed to enable this behavior
-# Gcc 4.x and above do not need any option but will still complain about unknown
-# options if another warning or error happens, and as such they're not testable.
-# Clang needs a special option -Wno-unknown-warning-option. Compilers not
-# supporting this option will check all warnings individually.
-cc-anywno := $(call cc-opt,-Wno-haproxy-warning)
-cc-wnouwo := $(if $(cc-anywno),,$(call cc-opt,-Wno-unknown-warning-option))
-cc-anywno := $(if $(cc-anywno)$(cc-wnouwo),1)
-
-# Disable a warning when supported by the compiler. Don't put spaces around the
-# warning! And don't use cc-opt which doesn't always report an error until
-# another one is also returned. If "cc-anywno" is set, the compiler supports
-# -Wno- followed by anything so we don't even need to start the compiler.
-# Usage: CFLAGS += $(call cc-nowarn,warning). Eg: $(call cc-opt,format-truncation)
-cc-nowarn = $(if $(cc-anywno),-Wno-$(1),$(shell set -e; if $(CC) -Werror -W$(1) -E -xc - -o /dev/null </dev/null >&0 2>/dev/null; then echo "-Wno-$(1)"; fi;))
 
 #### Installation options.
 DESTDIR =

include/make/compiler.mk

@@ -0,0 +1,42 @@
+# WARNING: Do not change cc-opt, cc-opt-alt or cc-warning without checking if
+#          clang bug #49364 is fixed. stderr is redirected to /dev/null on
+#          purpose, to work around a clang 11 bug that crashes if stderr is
+#          redirected to stdin.
+#
+# Function used to detect support of a given option by the compiler.
+# Usage: CFLAGS += $(call cc-opt,option). Eg: $(call cc-opt,-fwrapv)
+# Note: ensure the referencing variable is assigned using ":=" and not "=" to
+#       call it only once.
+cc-opt = $(shell set -e; if $(CC) -Werror $(1) -E -xc - -o /dev/null </dev/null >&0 2>/dev/null; then echo "$(1)"; fi;)
+
+# same but tries with $2 if $1 is not supported
+cc-opt-alt = $(if $(shell set -e; if $(CC) -Werror $(1) -E -xc - -o /dev/null </dev/null >&0 2>/dev/null; then echo 1;fi),$(1),$(call cc-opt,$(2)))
+
+# validate a list of options one at a time
+cc-all-opts  = $(foreach a,$(1),$(call cc-opt,$(a)))
+
+# try to pass plenty of options at once, take them on success or try them
+# one at a time on failure and keep successful ones. This is handy to quickly
+# validate most common options.
+cc-all-fast = $(if $(call cc-opt,$(1)),$(1),$(call cc-all-opts,$(1)))
+
+# Below we verify that the compiler supports any -Wno-something option to
+# disable any warning, or if a special option is needed to achieve that. This
+# will allow to get rid of testing when the compiler doesn't care. The result
+# is made of two variables:
+#  - cc-anywno that's non-empty if the compiler supports disabling anything
+#  - cc-wnouwo that may contain an option needed to enable this behavior
+# Gcc 4.x and above do not need any option but will still complain about unknown
+# options if another warning or error happens, and as such they're not testable.
+# Clang needs a special option -Wno-unknown-warning-option. Compilers not
+# supporting this option will check all warnings individually.
+cc-anywno := $(call cc-opt,-Wno-haproxy-warning)
+cc-wnouwo := $(if $(cc-anywno),,$(call cc-opt,-Wno-unknown-warning-option))
+cc-anywno := $(if $(cc-anywno)$(cc-wnouwo),1)
+
+# Disable a warning when supported by the compiler. Don't put spaces around the
+# warning! And don't use cc-opt which doesn't always report an error until
+# another one is also returned. If "cc-anywno" is set, the compiler supports
+# -Wno- followed by anything so we don't even need to start the compiler.
+# Usage: CFLAGS += $(call cc-nowarn,warning). Eg: $(call cc-opt,format-truncation)
+cc-nowarn = $(if $(cc-anywno),-Wno-$(1),$(shell set -e; if $(CC) -Werror -W$(1) -E -xc - -o /dev/null </dev/null >&0 2>/dev/null; then echo "-Wno-$(1)"; fi;))