tests: posix: tests for environ, getenv, setenv, unsetenv

Add tests for environ, getenv(), setenv(), unsetenv(), and
getenv_r().

Signed-off-by: Christopher Friedt <cfriedt@meta.com>

tests/posix/env/testcase.yaml

@@ -0,0 +1,32 @@
+common:
+  filter: not CONFIG_NATIVE_LIBC
+  arch_exclude:
+    - posix
+  integration_platforms:
+    - qemu_riscv64
+  tags: posix
+tests:
+  portability.posix.env: {}
+  portability.posix.env.armclang_std_libc:
+    toolchain_allow: armclang
+    extra_configs:
+      - CONFIG_ARMCLANG_STD_LIBC=y
+  portability.posix.env.arcmwdtlib:
+    toolchain_allow: arcmwdt
+    extra_configs:
+      - CONFIG_ARCMWDT_LIBC=y
+  portability.posix.env.minimal:
+    extra_configs:
+      - CONFIG_MINIMAL_LIBC=y
+      - CONFIG_COMMON_LIBC_MALLOC_ARENA_SIZE=256
+  portability.posix.env.newlib:
+    platform_exclude:
+      - hifive1
+    filter: TOOLCHAIN_HAS_NEWLIB == 1
+    extra_configs:
+      - CONFIG_NEWLIB_LIBC=y
+  portability.posix.env.picolibc:
+    tags: picolibc
+    filter: CONFIG_PICOLIBC_SUPPORTED
+    extra_configs:
+      - CONFIG_PICOLIBC=y