build system: FEATURE_LIBBUSYBOX_STATIC - try to pull libc/libm into libbusybox

It variously fails with different toolchains I tried...

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

Config.in

@@ -386,29 +386,26 @@ config BUILD_LIBBUSYBOX
 	  Build a shared library libbusybox.so.N.N.N which contains all
 	  busybox code.
 
-	  This feature allows every applet to be built as a tiny
-	  separate executable. Enabling it for "one big busybox binary"
-	  approach serves no purpose and increases code size.
-	  You should almost certainly say "no" to this.
+	  This feature allows every applet to be built as a really tiny
+	  separate executable linked against the library:
 
-### config FEATURE_FULL_LIBBUSYBOX
-###	bool "Feature-complete libbusybox"
-###	default n if !FEATURE_SHARED_BUSYBOX
-###	depends on BUILD_LIBBUSYBOX
-###	help
-###	  Build a libbusybox with the complete feature-set, disregarding
-###	  the actually selected config.
-###
-###	  Normally, libbusybox will only contain the features which are
-###	  used by busybox itself. If you plan to write a separate
-###	  standalone application which uses libbusybox say 'Y'.
-###
-###	  Note: libbusybox is GPL, not LGPL, and exports no stable API that
-###	  might act as a copyright barrier. We can and will modify the
-###	  exported function set between releases (even minor version number
-###	  changes), and happily break out-of-tree features.
-###
-###	  Say 'N' if in doubt.
+	  $ size 0_lib/l*
+	    text  data	 bss     dec    hex filename
+	     939   212	  28    1179    49b 0_lib/last
+	     939   212	  28    1179    49b 0_lib/less
+	  919138  8328  1556  929022  e2cfe 0_lib/libbusybox.so.1.N.M
+
+	  This is useful on NOMMU systems which are not capable
+	  of sharing executables, but are capable of sharing code
+	  in dynamic libraries.
+
+config FEATURE_LIBBUSYBOX_STATIC
+	bool "Pull in all external references into libbusybox"
+	default n
+	depends on BUILD_LIBBUSYBOX
+	help
+	  Make libbusybox library independent, not using or requiring
+	  any other shared libraries.
 
 config FEATURE_INDIVIDUAL
 	bool "Produce a binary for each applet, linked against libbusybox"

scripts/trylink

@@ -91,7 +91,9 @@ fi
 
 START_GROUP="-Wl,--start-group"
 END_GROUP="-Wl,--end-group"
-INFO_OPTS="-Wl,--warn-common -Wl,-Map,$EXE.map -Wl,--verbose"
+INFO_OPTS() {
+	echo "-Wl,--warn-common -Wl,-Map,$EXE.map -Wl,--verbose"
+}
 
 # gold may not support --sort-common (yet)
 SORT_COMMON="-Wl,--sort-common"
@@ -194,7 +196,7 @@ if ! test -f busybox_ldscript; then
 	    $GC_SECTIONS \
 	    $START_GROUP $O_FILES $A_FILES $END_GROUP \
 	    $l_list \
-	    $INFO_OPTS \
+	    `INFO_OPTS` \
     || {
 	cat $EXE.out
 	exit 1
@@ -225,7 +227,7 @@ else
 	    -Wl,-T,busybox_ldscript \
 	    $START_GROUP $O_FILES $A_FILES $END_GROUP \
 	    $l_list \
-	    $INFO_OPTS \
+	    `INFO_OPTS` \
     || {
 	cat $EXE.out
 	exit 1
@@ -244,10 +246,14 @@ if test "$CONFIG_BUILD_LIBBUSYBOX" = y; then
     }
     ln -s "libbusybox.so.$BB_VER" "$sharedlib_dir"/libbusybox.so 2>/dev/null
 
+    # Yes, "ld -shared -static" is a thing. It's a shared library which is itself static.
+    LBB_STATIC=""
+    test "$CONFIG_FEATURE_LIBBUSYBOX_STATIC" = y && LBB_STATIC="-Wl,-static"
+
     EXE="$sharedlib_dir/libbusybox.so.${BB_VER}_unstripped"
     try $CC $CFLAGS $LDFLAGS \
 	    -o $EXE \
-	    -shared -fPIC \
+	    -shared -fPIC $LBB_STATIC \
 	    -Wl,--enable-new-dtags \
 	    -Wl,-z,combreloc \
 	    -Wl,-soname="libbusybox.so.$BB_VER" \
@@ -256,7 +262,7 @@ if test "$CONFIG_BUILD_LIBBUSYBOX" = y; then
 	    $SORT_SECTION \
 	    $START_GROUP $A_FILES $END_GROUP \
 	    $l_list \
-	    $INFO_OPTS \
+	    `INFO_OPTS` \
     || {
 	echo "Linking $EXE failed"
 	cat $EXE.out
@@ -277,7 +283,7 @@ if test "$CONFIG_FEATURE_SHARED_BUSYBOX" = y; then
 	    $START_GROUP $O_FILES $END_GROUP \
 	    -L"$sharedlib_dir" -lbusybox \
 	    $l_list \
-	    $INFO_OPTS \
+	    `INFO_OPTS` \
     || {
 	echo "Linking $EXE failed"
 	cat $EXE.out