Examples makefiles: align /usr/local with /src Makefile (#4286)

* align /usr/local with src Makefile

Align /usr/local with the /src Makefile, where it can be overriden.

* /usr/local: allow override

align /usr/local with the /src Makefile, where it can be overriden

examples/Makefile

@@ -70,8 +70,9 @@ RAYLIB_SRC_PATH       ?= ../src
 
 # Locations of raylib.h and libraylib.a/libraylib.so
 # NOTE: Those variables are only used for PLATFORM_OS: LINUX, BSD
-RAYLIB_INCLUDE_PATH   ?= /usr/local/include
-RAYLIB_LIB_PATH       ?= /usr/local/lib
+DESTDIR ?= /usr/local
+RAYLIB_INCLUDE_PATH   ?= $(DESTDIR)/include
+RAYLIB_LIB_PATH       ?= $(DESTDIR)/lib
 
 # Library type compilation: STATIC (.a) or SHARED (.so/.dll)
 RAYLIB_LIBTYPE        ?= STATIC

examples/Makefile.Web

@@ -35,8 +35,9 @@ RAYLIB_PATH           ?= ..
 
 # Locations of raylib.h and libraylib.a/libraylib.so
 # NOTE: Those variables are only used for PLATFORM_OS: LINUX, BSD
-RAYLIB_INCLUDE_PATH   ?= /usr/local/include
-RAYLIB_LIB_PATH       ?= /usr/local/lib
+DESTDIR ?= /usr/local
+RAYLIB_INCLUDE_PATH   ?= $(DESTDIR)/include
+RAYLIB_LIB_PATH       ?= $(DESTDIR)/lib
 
 # Library type compilation: STATIC (.a) or SHARED (.so/.dll)
 RAYLIB_LIBTYPE        ?= STATIC