Failing to compile with ICU support error on Ubuntu

[Siddharth Karandikar <siddharth.karandikar@xxxxxxxxx>]

Hi,

I am trying to build the latest postgresql on my ubuntu docker instance. But its failing to compile it even when ICU related libraries are installed.

Compilation fails with 

```

checking whether to build with ICU support... yes

checking for icu-uc icu-i18n... no

configure: error: ICU library not found

If you have ICU already installed, see config.log for details on the

failure.  It is possible the compiler isn't looking in the proper directory.

Use --without-icu to disable ICU support.

```

config.log has following error

```

configure:8442: error: ICU library not found

```

I am running on (my docker instance is)

```

$ cat /etc/lsb-release

DISTRIB_ID=Ubuntu

DISTRIB_RELEASE=23.04

DISTRIB_CODENAME=lunar

DISTRIB_DESCRIPTION="Ubuntu 23.04"

```

And when I checked, it looks like icu related libraries are there too

```

$ sudo apt-get install icu-devtools libicu-dev libicu72

Reading package lists... Done

Building dependency tree... Done

Reading state information... Done

icu-devtools is already the newest version (72.1-3ubuntu2).

libicu-dev is already the newest version (72.1-3ubuntu2).

libicu72 is already the newest version (72.1-3ubuntu2).

0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

```

I am pretty new to postgresql's source code and don't yet know whats the use of ICU libs. So I tried building it with --without-icu and it worked. But I am not able to figure out whats going wrong here with ICU libs. It would be good if I can get a proper, clean build.

Thanks,

Siddharth