--- libplist-2.3.0/configure.ac.orig	2023-04-21 14:07:43.000000000 +0200
+++ libplist-2.3.0/configure.ac	2023-11-25 21:12:09.871666005 +0100
@@ -179,7 +179,7 @@ esac],
 
 if (test "x$debug" = "xyes"); then
        AC_DEFINE(DEBUG, 1, [Define if debug message output code should be built.])
-       GLOBAL_CFLAGS+=" -g"
+       GLOBAL_CFLAGS="$GLOBAL_CFLAGS -g"
 fi
 
 AC_SUBST(GLOBAL_CFLAGS)
@@ -211,23 +211,23 @@ fi
 
 if test "x$build_sanitizers" = "xyes"; then
     AS_COMPILER_FLAG([-fsanitize=address], [
-        SANITIZER_FLAGS+=" -fsanitize=address"
+        SANITIZER_FLAGS="$SANITIZER_FLAGS -fsanitize=address"
         ASAN_AVAILABLE=yes
     ], [])
     if test "$ASAN_AVAILABLE" = "yes"; then
         AS_COMPILER_FLAG([-fsanitize=address -fsanitize-address-use-after-scope], [
-            SANITIZER_FLAGS+=" -fsanitize-address-use-after-scope"
+            SANITIZER_FLAGS="$SANITIZER_FLAGS -fsanitize-address-use-after-scope"
         ], [])
-        SANITIZERS+="ASAN "
+        SANITIZERS="${SANITIZERS}ASAN "
     fi
 
     AS_COMPILER_FLAG([-fsanitize=undefined], [
-        SANITIZER_FLAGS+=" -fsanitize=undefined"
+        SANITIZER_FLAGS="$SANITIZER_FLAGS -fsanitize=undefined"
         UBSAN_AVAILABLE=yes
     ], [])
 
     if test "$UBSAN_AVAILABLE" = "yes"; then
-        SANITIZERS+="UBSAN "
+        SANITIZERS="${SANITIZERS}UBSAN "
     fi
 
     if test -z "$SANITIZER_FLAGS"; then
@@ -240,13 +240,13 @@ if test "x$build_sanitizers" = "xyes"; t
             if test -z "$SAN_COV_FLAGS"; then
                 SAN_COV_FLAGS="$COV_CHECK"
             else
-                SAN_COV_FLAGS+=",$COV_CHECK"
+                SAN_COV_FLAGS="${SAN_COV_FLAGS},$COV_CHECK"
             fi
         ], [])
     done
     if test -n "$SAN_COV_FLAGS"; then
-        SANITIZER_FLAGS+=" -fsanitize-coverage=$SAN_COV_FLAGS"
-        SANITIZERS+="+coverage "
+        SANITIZER_FLAGS="$SANITIZER_FLAGS -fsanitize-coverage=$SAN_COV_FLAGS"
+        SANITIZERS="${SANITIZERS}+coverage "
     else
         AC_MSG_WARN([No sanitizer coverage supported by compiler])
     fi
@@ -254,20 +254,20 @@ if test "x$build_sanitizers" = "xyes"; t
     CFLAGS="-O1"
 
     AS_COMPILER_FLAG([-fno-omit-frame-pointer], [
-        CFLAGS+=" -fno-omit-frame-pointer"
+        CFLAGS="$CFLAGS -fno-omit-frame-pointer"
     ], [])
 
     AS_COMPILER_FLAG([-gline-tables-only], [
-        CFLAGS+=" -gline-tables-only"
+        CFLAGS="$CFLAGS -gline-tables-only"
     ],
     [
-        CFLAGS+=" -g"
+        CFLAGS="$CFLAGS -g"
     ])
 
-    EXTRA_CONF+="  Enabled sanitizers ......: $SANITIZERS
+    EXTRA_CONF="$EXTRA_CONF  Enabled sanitizers ......: $SANITIZERS
 "
 
-    CFLAGS+=" $SANITIZER_FLAGS"
+    CFLAGS="$CFLAGS $SANITIZER_FLAGS"
     CXXFLAGS="$CFLAGS -std=c++11"
 fi
 
@@ -281,9 +281,9 @@ if test "x$build_fuzzers" = "xyes"; then
         ;;
     esac
 
-    CFLAGS+=" -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION"
+    CFLAGS="$CFLAGS -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION"
 
-    EXTRA_CONF+="  Build fuzzers ...........: yes
+    EXTRA_CONF="$EXTRA_CONF  Build fuzzers ...........: yes
 "
 fi