Enable -ffreestanding by default

Fixes #5429

repos/base-linux/lib/import/import-syscall-linux.mk

@@ -25,3 +25,7 @@ HOST_INC_DIR += /usr/include/aarch64-linux-gnu
 #
 CC_OPT += -D_GNU_SOURCE
 
+#
+# Enable definition of __STDC_HOSTED__
+#
+CC_OPT_FREESTANDING =

repos/base/mk/global.mk

@@ -98,6 +98,11 @@ ifneq ($(STDLIB),yes)
 LD_OPT_NOSTDLIB := -nostdlib -Wl,-nostdlib
 endif
 
+#
+# Prevent the definition of __STDC_HOSTED__ by default
+#
+CC_OPT_FREESTANDING ?= -ffreestanding
+
 #
 # Add coverage options
 #
@@ -166,7 +171,8 @@ CC_ADA_WARN        ?= -gnatwa $(CC_ADA_WARN_STRICT)
 #
 # Aggregate compiler options that are common for C and C++
 #
-CC_OPT += $(CC_OPT_NOSTDINC) -g $(CC_MARCH) $(CC_OLEVEL) $(CC_OPT_DEP) $(CC_WARN)
+CC_OPT += $(CC_OPT_NOSTDINC) $(CC_OPT_FREESTANDING) -g \
+          $(CC_MARCH) $(CC_OLEVEL) $(CC_OPT_DEP) $(CC_WARN)
 
 #
 # Incorporate source-file-specific compiler options

repos/libports/lib/import/import-libc.mk

@@ -51,6 +51,11 @@ endif
 #
 REP_INC_DIR += include/libc-genode
 
+#
+# Enable definition of __STDC_HOSTED__
+#
+CC_OPT_FREESTANDING =
+
 #
 # Prevent gcc headers from defining __size_t. This definition is done in
 # machine/_types.h.