- add a macro to check for ld and as flags

Very unreliable as e.g the ld check will see the flags supported by each emulation, not just the active one.
  good enough for now..
  Fix would be to crate one or more dummy .c files and accually try if a flag
  works.

Makefile

@@ -277,8 +277,7 @@ endif
 	$(CC) $(CFLAGS) $(EXTRA_CFLAGS) $(LDFLAGS) -shared \
 	$(CFLAGS_PIC) \
 	-Wl,-soname=$(LD_LIBBUSYBOX).$(MAJOR_VERSION) \
-	-Wl,--enable-new-dtags -Wl,--reduce-memory-overheads \
+	-Wl,-z,combreloc $(LIB_LDFLAGS) \
-	-Wl,-z,combreloc -Wl,-shared -Wl,--as-needed -Wl,--warn-shared-textrel \
 	-o $(@) \
 	-Wl,--start-group -Wl,--whole-archive \
 	$(LIBRARY_DEFINE) $(^) \

Rules.mak

@@ -115,6 +115,20 @@ check_gcc=$(shell \
 		then echo "$(1)"; else echo "$(2)"; fi \
 	fi)
 
+# A not very robust macro to check for available ld flags
+check_ld=$(shell \
+	echo "checking='$(1)'" >> foo.txt ; \
+	if [ "x$(1)" != "x" ]; then \
+		$(LD) --help | grep -q \\$(1) && echo "-Wl,$(1)$(2)" ; \
+	fi)
+
+# A not very robust macro to check for available as flags
+check_as=$(shell \
+	if [ "x$(1)" != "x" ]; then \
+		$(AS) --help | grep -q "\\$(1)" && echo "-Wa,$(1)$(2)" ; \
+	fi)
+
+
 # Setup some shortcuts so that silent mode is silent like it should be
 ifeq ($(subst s,,$(MAKEFLAGS)),$(MAKEFLAGS))
 export MAKE_IS_SILENT=n
@@ -145,10 +159,15 @@ OPTIMIZATION+=$(call check_gcc,-funit-at-a-time,)
 PROG_CFLAGS+=$(call check_gcc,-fwhole-program,)
 endif # CONFIG_BUILD_AT_ONCE
 
+LIB_LDFLAGS:=$(call check_ld,--enable-new-dtags,)
+#LIB_LDFLAGS+=$(call check_ld,--reduce-memory-overheads,)
+#LIB_LDFLAGS+=$(call check_ld,--as-needed,)
+#LIB_LDFLAGS+=$(call check_ld,--warn-shared-textrel,)
+
+
 # Some nice architecture specific optimizations
 ifeq ($(strip $(TARGET_ARCH)),arm)
 	OPTIMIZATION+=-fstrict-aliasing
-	OPTIMIZATION+=$(call check_gcc,-msingle-pic-base,)
 endif
 ifeq ($(strip $(TARGET_ARCH)),i386)
 	OPTIMIZATION+=$(call check_gcc,-march=i386,)
@@ -169,7 +188,7 @@ ifeq ($(strip $(shell [ $(CC_MAJOR) -ge 4 -a $(CC_MINOR) -ge 1 ] ; echo $$?)),0)
 	OPTIMIZATION+=$(call check_gcc,-fno-branch-count-reg,)
 endif # gcc-4.1 and beyond
 endif
-OPTIMIZATIONS:=$(OPTIMIZATION) -fomit-frame-pointer
+OPTIMIZATIONS:=$(OPTIMIZATION) $(call check_gcc,-fomit-frame-pointer,)
 
 #
 #--------------------------------------------------------
@@ -195,21 +214,22 @@ else
 endif
 ifeq ($(strip $(CONFIG_DEBUG)),y)
     CFLAGS  +=$(WARNINGS) -g -D_GNU_SOURCE
-    LDFLAGS +=-Wl,-warn-common
+    LDFLAGS += $(call check_ld,-warn-common,)
     STRIPCMD:=/bin/true -Not_stripping_since_we_are_debugging
 else
     CFLAGS+=$(WARNINGS) $(OPTIMIZATIONS) -D_GNU_SOURCE -DNDEBUG
-    LDFLAGS += -Wl,-warn-common -Wl,--sort-common 
+    LDFLAGS += $(call check_ld,-warn-common,)
+    LDFLAGS += $(call check_ld,--sort-common,)
     STRIPCMD:=$(STRIP) -s --remove-section=.note --remove-section=.comment
 endif
 ifeq ($(strip $(CONFIG_STATIC)),y)
-    LDFLAGS += --static
+    LDFLAGS += $(call check_ld,--static,)
 #else
 #    LIBRARIES += -ldl
 endif
 
 ifeq ($(strip $(CONFIG_BUILD_LIBBUSYBOX)),y)
-    CFLAGS_PIC:= -fPIC #-DPIC
+    CFLAGS_PIC:= $(call check_gcc,-fPIC,)
 endif
 
 ifeq ($(strip $(CONFIG_SELINUX)),y)