[openwrt/openwrt] build, imagebuilder: Do not require compilers

[LEDE Commits]

aparcar pushed a commit to openwrt/openwrt.git, branch openwrt-19.07:
https://git.openwrt.org/79b1fa170288115d1929c55713dc840a133bddd9

commit 79b1fa170288115d1929c55713dc840a133bddd9
Author: Sven Roederer <devel-sven at geroedel.de>
AuthorDate: Sun Sep 27 23:07:38 2020 +0200

    build, imagebuilder: Do not require compilers
    
    The buildroot and SDK both require the compilers (gcc, g++) to be
    installed on the host system, however the ImageBuilder uses precompiled
    binaries.
    
    This patch changes the prerequirements checks to skip the checking for
    the compilers if running as ImageBuilder. A similar change has been
    made for libncurses-dev in 4a1a58a3e2d2.
    
    Signed-off-by: Sven Roederer <devel-sven at geroedel.de>
    Acked-by: Paul Spooren <mail at aparcar.org>
    (cherry picked from commit ae12a747cae3df16d84b7dc92f39427948d4e8e2)
---
 include/prereq-build.mk | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/prereq-build.mk b/include/prereq-build.mk
index 622db96ee3..7504d43a74 100644
--- a/include/prereq-build.mk
+++ b/include/prereq-build.mk
@@ -26,6 +26,7 @@ $(eval $(call TestHostCommand,proper-umask, \
 	Please build with umask 022 - other values produce broken packages, \
 	umask | grep -xE 0?0[012][012]))
 
+ifndef IB
 $(eval $(call SetupHostCommand,gcc, \
 	Please install the GNU C Compiler (gcc) 4.8 or later, \
 	$(CC) -dumpversion | grep -E '^(4\.[8-9]|[5-9]\.?|10\.?)', \
@@ -37,7 +38,9 @@ $(eval $(call TestHostCommand,working-gcc, \
 	it appears to be broken, \
 	echo 'int main(int argc, char **argv) { return 0; }' | \
 		gcc -x c -o $(TMP_DIR)/a.out -))
+endif
 
+ifndef IB
 $(eval $(call SetupHostCommand,g++, \
 	Please install the GNU C++ Compiler (g++) 4.8 or later, \
 	$(CXX) -dumpversion | grep -E '^(4\.[8-9]|[5-9]\.?|10\.?)', \
@@ -50,6 +53,7 @@ $(eval $(call TestHostCommand,working-g++, \
 	echo 'int main(int argc, char **argv) { return 0; }' | \
 		g++ -x c++ -o $(TMP_DIR)/a.out - -lstdc++ && \
 		$(TMP_DIR)/a.out))
+endif
 
 ifndef IB
 $(eval $(call TestHostCommand,ncurses, \