fixes linux build(gcc16) with linux build make command

[flipchan]

This fixes building on linux and the latest fedora kernels with gcc16

Problem

Rapidsnark failed to compile on systems with GCC 16 due to two issues:

1. GMP 6.3.0 configure fails — The "long long reliability test 1" in GMP's configure uses -pedantic, which GCC 16 rejects because of stricter enforcement of forward declaration argument matching.

2. Missing #include <cstdint> — GCC 16 no longer transitively includes <cstdint> from standard library headers like <string>, <memory>, etc. Files using uint32_t, uint64_t, etc. without a direct or transitive path to <cstdint> fail to compile.

Changes

1. Conditional #include <cstdint> behind BUILD_LINUX CMake flag

The cstdint includes are only added when building with -DBUILD_LINUX=ON, which defines RAPIDSNARK_LINUX. This keeps the fix scoped to Linux builds and avoids touching other platforms.

CMakeLists.txt (src/CMakeLists.txt):

option(BUILD_LINUX "Build for Linux (adds cstdint includes needed by GCC 16+)" OFF)
if(BUILD_LINUX)
    add_definitions(-DRAPIDSNARK_LINUX)
endif()

Source files — each guarded with #ifdef RAPIDSNARK_LINUX:

• src/binfile_utils.hpp — #include <cstdint> after <memory> include
• src/binfile_utils.cpp — #include <cstdint> before project includes
• src/zkey_utils.cpp — #include <cstdint> before <stdexcept> include
• src/random_generator.hpp — #include <cstdint> after <random> include

Usage:

make host_linux

2. Workaround for GMP build (not a code change)

The build_gmp.sh host target fails because GMP's configure adds -pedantic which triggers an error in GCC 16's long long reliability test. Workaround:

cd depends/gmp
rm -rf build && mkdir build && cd build
../configure --prefix="$PWD/../../package" \
  --with-pic --disable-fft --enable-fat \
  CFLAGS="-O2 -fomit-frame-pointer -m64 -Wno-error" \
  CC="gcc -std=gnu11"
make -j$(nproc) && make install

The -std=gnu11 flag allows the test code (which uses implicit function declarations) to compile without error.

Notes

• Only 4 files needed cstdint fixes. All other source files either already included it directly (7 files) or received it transitively through fr_element.hpp / fq_element.hpp / misc.hpp (8 files).
• The non-standard u_int32_t / u_int64_t types (BSD extensions from <sys/types.h>) used in binfile_utils, zkey_utils, groth16, etc. remain unchanged — they compile on Linux via system header transitive includes but are a separate portability concern.

[flipchan]

ping @olomix this fixes linux builds, looks green :)