--- rsblib/configure.orig	2022-02-01 02:31:47 UTC
+++ rsblib/configure
@@ -16350,7 +16350,7 @@ if test x"$want_rsblib" != x"no" ; then
 	LIBRSB_LOCAL_LIBS="${BPWD}/librsb.la";
 	{ $as_echo "$as_me:${as_lineno-$LINENO}: Assuming building as subdir of librsb, and that librsb will be built later." >&5
 $as_echo "$as_me: Assuming building as subdir of librsb, and that librsb will be built later." >&6;}
-	CPPFLAGS+=" -I${BPWD}"
+	CPPFLAGS="${CPPFLAGS} -I${BPWD}"
 	ac_cv_func_rsb_lib_init="yes";
 else
 
@@ -16438,9 +16438,9 @@ fi
 $as_echo "$as_me: Where is librsb-config ?" >&6;};
 	else
 		want_rsblib=yes;
-		CPPFLAGS+=" ` $LIBRSB_CONFIG --I_opts`"
-		LDFLAGS+=" `$LIBRSB_CONFIG --ldflags`"
-		LIBS+=" `$LIBRSB_CONFIG --libs --extra_libs`"
+		CPPFLAGS="${CPPFLAGS} ` $LIBRSB_CONFIG --I_opts`"
+		LDFLAGS="${LDFLAGS} `$LIBRSB_CONFIG --ldflags`"
+		LIBS="${LIBS} `$LIBRSB_CONFIG --libs --extra_libs`"
 	fi
 	for ac_header in rsb.h
 do :
@@ -16538,7 +16538,7 @@ fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_pthread_pthread_cancel" >&5
 $as_echo "$ac_cv_lib_pthread_pthread_cancel" >&6; }
 if test "x$ac_cv_lib_pthread_pthread_cancel" = xyes; then :
-  LIBS+=" -lpthread";
+  LIBS="${LIBS} -lpthread";
 fi
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for main in -lgtest" >&5
@@ -16680,14 +16680,14 @@ fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_stdcppfs_main" >&5
 $as_echo "$ac_cv_lib_stdcppfs_main" >&6; }
 if test "x$ac_cv_lib_stdcppfs_main" = xyes; then :
-  RGT_LDADD+=" -lstdc++fs";
+  RGT_LDADD="${RGT_LDADD} -lstdc++fs";
 fi
  else
 	rsb_have_gtest=0;
 fi
 if test x"$want_rsblib" != x"no" ; then
 	# adding this now: assuming configure called *before* librsb.la built.
-	LIBS+=" ${LIBRSB_LOCAL_LIBS}"
+	LIBS="${LIBS} ${LIBRSB_LOCAL_LIBS}"
 fi
 RGT_LDADD="$RGT_LDADD"