[openwrt/openwrt] build: Improve GCC version detection

[LEDE Commits]

hauke pushed a commit to openwrt/openwrt.git, branch master:
https://git.lede-project.org/d6d3db05436952f68f47d35df58ad5050b1f2d66

commit d6d3db05436952f68f47d35df58ad5050b1f2d66
Author: Hauke Mehrtens <hauke at hauke-m.de>
AuthorDate: Sat Mar 31 21:28:32 2018 +0200

    build: Improve GCC version detection
    
    This now makes sure that the beginning of the version number gets checked
    and "4.4.5" will not match was a supported version.
    GCC 8 and GCC 9 are now marked as supported, but we probably have to fix
    some problems for them.
    
    Closes: FS#1433
    Signed-off-by: Hauke Mehrtens <hauke at hauke-m.de>
---
 include/prereq-build.mk | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/prereq-build.mk b/include/prereq-build.mk
index 6a423d2..6917716 100644
--- a/include/prereq-build.mk
+++ b/include/prereq-build.mk
@@ -28,13 +28,15 @@ $(eval $(call TestHostCommand,proper-umask, \
 
 $(eval $(call SetupHostCommand,gcc, \
 	Please install the GNU C Compiler (gcc) 4.8 or later \
-	$(CC) -dumpversion | grep -E '(4\.[8-9]|5\.?[0-9]?|6\.?[0-9]?|7\.?[0-9]?)', \
-	gcc -dumpversion | grep -E '(4\.[8-9]|5\.?[0-9]?|6\.?[0-9]?|7\.?[0-9]?)', \
+	$(CC) -dumpversion | grep -E '^(4\.[8-9]|[5-9]\.?)', \
+	gcc -dumpversion | grep -E '^(4\.[8-9]|[5-9]\.?)', \
 	gcc48 --version | grep gcc, \
 	gcc49 --version | grep gcc, \
 	gcc5 --version | grep gcc, \
 	gcc6 --version | grep gcc, \
 	gcc7 --version | grep gcc, \
+	gcc8 --version | grep gcc, \
+	gcc9 --version | grep gcc, \
 	gcc --version | grep Apple.LLVM ))
 
 $(eval $(call TestHostCommand,working-gcc, \
@@ -45,13 +47,15 @@ $(eval $(call TestHostCommand,working-gcc, \
 
 $(eval $(call SetupHostCommand,g++, \
 	Please install the GNU C++ Compiler (g++) 4.8 or later \
-	$(CXX) -dumpversion | grep -E '(4\.[8-9]|5\.?[0-9]?|6\.?[0-9]?|7\.?[0-9]?)', \
-	g++ -dumpversion | grep -E '(4\.[8-9]|5\.?[0-9]?|6\.?[0-9]?|7\.?[0-9]?)', \
+	$(CXX) -dumpversion | grep -E '^(4\.[8-9]|[5-9]\.?)', \
+	g++ -dumpversion | grep -E '^(4\.[8-9]|[5-9]\.?)', \
 	g++48 --version | grep g++, \
 	g++49 --version | grep g++, \
 	g++5 --version | grep g++, \
 	g++6 --version | grep g++, \
 	g++7 --version | grep g++, \
+	g++8 --version | grep g++, \
+	g++9 --version | grep g++, \
 	g++ --version | grep Apple.LLVM ))
 
 $(eval $(call TestHostCommand,working-g++, \