updated Makefile and PKGBUILD

Makefile

@@ -2,10 +2,14 @@ CC = gcc
 CFLAGS = -Wall -std=c17
 OUT = pwdgen
 SRC = src/*.c
+BUILDDIR=build
 DESTDIR = /usr/local/bin
 
 build:
-	@$(CC) $(CFLAGS) $(SRC) -o out/$(OUT)
+	@if [ ! -d ${BUILDDIR} ]; then \
+		mkdir -pv ${BUILDDIR}; \
+	fi
+	@$(CC) $(CFLAGS) $(SRC) -o ${BUILDDIR}/$(OUT)
 
 all:
 	@make clean
@@ -13,10 +17,15 @@ all:
 	@make run
 
 run:
-	@./out/$(OUT)
+	@./${BUILDDIR}/$(OUT)
 
 clean:
-	@rm -rf out/$(OUT)
+	@if [ -d ${BUILDDIR} ]; then \
+		rm -rv ${BUILDDIR}; \
+	fi
 
 install:
-	@cp -rf out/$(OUT) $(DESTDIR)
+	@if [ ! -d ${DESTDIR} ]; then \
+		mkdir -pv ${DESTDIR}; \
+	fi
+	@cp -rf ${BUILDDIR}/$(OUT) $(DESTDIR)