package/newlib-bare-metal: fix build without makeinfo

Fix the following build failure without makeinfo raised since the
addition of the package in commit
3b95ff658bf4859eb5cffd28cbbedd1826fad9a6:

make[5]: Entering directory '/home/buildroot/autobuild/instance-2/output-1/build/newlib-bare-metal-4.4.0/microblazeel-xilinx-elf/libgloss'
  MAKEINFO ../.././libgloss/doc/porting.info
/home/buildroot/autobuild/instance-2/output-1/build/newlib-bare-metal-4.4.0/missing: line 81: makeinfo: command not found

Fixes: 3b95ff658bf4859eb5cffd28cbbedd1826fad9a6
 - http://autobuild.buildroot.org/results/23e6641cbce62258310c300f8aed5d6a76973d72

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/newlib-bare-metal/newlib-bare-metal.mk

@@ -18,6 +18,7 @@ NEWLIB_BARE_METAL_LICENSE_FILES = \
 
 NEWLIB_BARE_METAL_INSTALL_STAGING = YES
 NEWLIB_BARE_METAL_INSTALL_TARGET = NO
+NEWLIB_BARE_METAL_MAKE_OPTS = MAKEINFO=true
 
 define NEWLIB_BARE_METAL_CONFIGURE_CMDS
 	(cd $(@D) && \
@@ -34,11 +35,12 @@ define NEWLIB_BARE_METAL_CONFIGURE_CMDS
 endef
 
 define NEWLIB_BARE_METAL_BUILD_CMDS
-	PATH=$(BR_PATH) $(MAKE1) -C $(@D)
+	PATH=$(BR_PATH) $(MAKE1) $(NEWLIB_BARE_METAL_MAKE_OPTS) -C $(@D)
 endef
 
 define NEWLIB_BARE_METAL_INSTALL_STAGING_CMDS
-	PATH=$(BR_PATH) $(MAKE1) -C $(@D) DESTDIR=$(TOOLCHAIN_BARE_METAL_BUILDROOT_SYSROOT) install
+	PATH=$(BR_PATH) $(MAKE1) -C $(@D) $(NEWLIB_BARE_METAL_MAKE_OPTS) \
+		DESTDIR=$(TOOLCHAIN_BARE_METAL_BUILDROOT_SYSROOT) install
 endef
 
 define NEWLIB_BARE_METAL_FIXUP