[openwrt/openwrt] build, imagebuilder: Do not require libncurses-dev

[LEDE Commits]

aparcar pushed a commit to openwrt/openwrt.git, branch openwrt-19.07:
https://git.openwrt.org/58138df2d56789f0b3da3fe0592d9d1288803bcb

commit 58138df2d56789f0b3da3fe0592d9d1288803bcb
Author: Paul Spooren <mail at aparcar.org>
AuthorDate: Tue Apr 14 11:14:47 2020 -1000

    build, imagebuilder: Do not require libncurses-dev
    
    The buildroot and SDK both require `libncurses-dev` to be installed on
    the system, however the ImageBuilder uses precompiled binaries.
    
    This patch changes the prerequirements checks to skip the
    `libncurses-dev` part if running as ImageBuilder.
    
    Signed-off-by: Paul Spooren <mail at aparcar.org>
    (cherry picked from commit 4a1a58a3e2d2360950ff23a05f1f55b779174d6a)
---
 include/prereq-build.mk | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/prereq-build.mk b/include/prereq-build.mk
index 501739968c..622db96ee3 100644
--- a/include/prereq-build.mk
+++ b/include/prereq-build.mk
@@ -51,10 +51,12 @@ $(eval $(call TestHostCommand,working-g++, \
 		g++ -x c++ -o $(TMP_DIR)/a.out - -lstdc++ && \
 		$(TMP_DIR)/a.out))
 
+ifndef IB
 $(eval $(call TestHostCommand,ncurses, \
 	Please install ncurses. (Missing libncurses.so or ncurses.h), \
 	echo 'int main(int argc, char **argv) { initscr(); return 0; }' | \
 		gcc -include ncurses.h -x c -o $(TMP_DIR)/a.out - -lncurses))
+endif
 
 ifeq ($(HOST_OS),Linux)
   zlib_link_flags := -Wl,-Bstatic -lz -Wl,-Bdynamic