Can't find openjpeg.h when cross-compile.

[leimaohui]

When I upgrade openjpeg2.3.1(5709632) to openjpeg2.4.0(37ac30c), I met an issue as following when I compiled an OSS(poppler) which depends on openjpeg:
fatal error: openjpeg.h: No such file or directory | 20 | #include <openjpeg.h> | | ^~~~~~~~~~~~ | compilation terminated.
I found it is because the patch of Issue#1174. This patch fixes the include directory to /usr/include/openjpeg-2.4, but under cross-compile environment, openjpeg.h should be installed to "${CROSS_ENV}/usr/include/openjpeg-2.4/" instead of "/usr/include/openjpeg-2.4".

[rouault]

Fixed per pull request #1321