Partially adapted from Debian. Do not ignore LDFLAGS we set.
We do not want the -g part, as that is handled by xbps-src.

--- a/Makefile.in
+++ b/Makefile.in
@@ -99,13 +99,14 @@
 #target=x86_64-apple-darwin
 #target=i386-pc-mingw32
 
+SHLIB_FLAGS=$(LDFLAGS)
 ifeq ($(SOEXT),.so)
-SHLIB_FLAGS=-Wl,-soname,$@
+SHLIB_FLAGS+=-Wl,-soname,$@
 else ifeq ($(SOEXT),.dll)
-SHLIB_FLAGS=
+SHLIB_FLAGS+=
 else ifeq ($(SOEXT),.dylib)
 # Allow the use of -rpath in executable
-SHLIB_FLAGS=-Wl,-install_name,@rpath/$@
+SHLIB_FLAGS+=-Wl,-install_name,@rpath/$@
 endif
 
 # Flags for libraries
--- a/configure
+++ b/configure
@@ -16,7 +16,7 @@
 CFLAGS=${CFLAGS:--g}
 GNATMAKE=${GNATMAKE:-gnatmake}
 MAKE=${MAKE:-make}
-LDFLAGS=
+LDFLAGS=${LDFLAGS}
 prefix=/usr/local
 libdirsuffix=lib/ghdl
 incdirsuffix=include