README: Fedora: Add gcc, gcc-c++, cargo, and awk

This commit adds dependencies needed for `../gccrs/configure --prefix=$HOME/gccrs-install --disable-bootstrap --enable-multilib --enable-languages=rust` (from the README) in a fresh `FedoraLinux-43` WSL. Most are also needed in a `fedora` container (the exception is `awk`; it's present in the container but not WSL).

In other words, this commit fixes the following `configure` errors (truncated and combined):

```
configure: error: no acceptable C compiler found in $PATH
configure: error: *** A compiler with support for C++14 language features is required.
configure: error: cargo is required to build rust
./config.status: line 1194: awk: command not found
```

The goal is to eventually package `gccrs` in Copr (Fedora's AUR). Finding all the dependencies is a first step.

Signed-off-by: Osama Albahrani <[email protected]>

Author: osalbahr

README.md

@@ -48,7 +48,7 @@ $ apt install build-essential libgmp3-dev libmpfr-dev libmpc-dev flex bison auto
 Fetch dependencies for Fedora:
 
 ```bash
-$ dnf install autoconf automake dejagnu flex bison glibc-devel.{x86_64,i686} gmp-devel libmpc-devel mpfr-devel
+$ dnf install autoconf automake dejagnu flex bison glibc-devel.{x86_64,i686} gmp-devel libmpc-devel mpfr-devel gcc gcc-c++ cargo awk
 ```
 
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