makefile: use proper linker flags for C++ compiles

Add CFLAGS_SL flags for C++ compiles, which adds needed -fPIC linker
flag.

Reported-by: Oleksii Kliukin
Discussion: https://postgr.es/m/E4A49A6B-621B-4830-A374-970EBB7D1328@hintbits.com

Backpatch-through: 10 only

diff --git a/src/Makefile.shlib b/src/Makefile.shlib
index eb45daedc884798cef1411d64a982de4ab443ec3..342496eecd04314f82e38a4bf04b7593fffa9744 100644 (file)
--- a/src/Makefile.shlib
+++ b/src/Makefile.shlib
@@ -101,6 +101,7 @@ endif
 # Try to keep the sections in some kind of order, folks...
 
 override CFLAGS += $(CFLAGS_SL)
+override CXXFLAGS += $(CFLAGS_SL)
 ifdef SO_MAJOR_VERSION
 # libraries ought to use this to refer to versioned gettext domain names
 override CPPFLAGS += -DSO_MAJOR_VERSION=$(SO_MAJOR_VERSION)